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  4. How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot
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How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot

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  • R Raphawel

    @jsulm Oh right, so I don't think it will be useful for my application.

    Just to show my result:
    CSV used:

    Date/Time;Power Consumed (W);Energy Consumed (Wh);Cumulative Energy Consumed (Wh)
    09/21/2022 02:30 PM CEST;;;576
    09/21/2022 02:45 PM CEST;2,712;674;1,25
    09/21/2022 03:00 PM CEST;2,652;-866;384
    09/21/2022 03:15 PM CEST;240;1,088;1,472
    09/21/2022 03:30 PM CEST;120;38;1,51
    09/21/2022 03:45 PM CEST;132;33;1,543
    09/21/2022 04:00 PM CEST;156;52;1,595
    09/21/2022 04:15 PM CEST;132;33;1,628
    09/21/2022 04:30 PM CEST;228;46;1,674
    09/21/2022 04:45 PM CEST;144;38;1,712
    09/21/2022 05:00 PM CEST;168;36;1,748
    09/21/2022 05:15 PM CEST;144;50;1,798
    09/21/2022 05:30 PM CEST;144;35;1,833
    09/21/2022 05:45 PM CEST;240;50;1,883
    09/21/2022 06:00 PM CEST;132;35;1,918
    09/21/2022 06:15 PM CEST;168;31;1,949
    09/21/2022 06:30 PM CEST;84;33;1,982
    09/21/2022 06:45 PM CEST;96;23;2,005
    09/21/2022 07:00 PM CEST;132;38;2,043
    09/21/2022 07:15 PM CEST;84;22;2,065
    09/21/2022 07:30 PM CEST;192;48;2,113
    09/21/2022 07:45 PM CEST;132;32;2,145
    09/21/2022 08:00 PM CEST;1,08;156;2,301
    09/21/2022 08:15 PM CEST;168;102;2,403
    09/21/2022 08:30 PM CEST;264;50;2,453
    09/21/2022 08:45 PM CEST;156;45;2,498
    09/21/2022 09:00 PM CEST;216;45;2,543
    09/21/2022 09:15 PM CEST;156;48;2,591
    09/21/2022 09:30 PM CEST;216;44;2,635
    09/21/2022 09:45 PM CEST;156;51;2,686
    09/21/2022 10:00 PM CEST;180;40;2,726
    09/21/2022 10:15 PM CEST;144;49;2,775
    09/21/2022 10:30 PM CEST;132;30;2,805
    09/21/2022 10:45 PM CEST;108;42;2,847
    09/21/2022 11:00 PM CEST;108;25;2,872
    09/21/2022 11:15 PM CEST;108;43;2,915
    

    Code (To identify the empty fields, I replaced :

    QStringList champs = ligne.split(";",QString::SkipEmptyParts);
    

    by :

    QStringList champs = ligne.split(";", QString::KeepEmptyParts);
    

    Code :

    void MainWindow::LireFichierCSV()
    {
    
        QStandardItemModel *model= new QStandardItemModel();
    
        QStringList location = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);  // Viens lire tout les fichiers du répertoire Document, mettre ::DesktopLocation pour le bureau
        QString result = location[0];
        result = result + QString("/system_meter_conso.csv");
        QFile file(result);
    
        if(file.open(QFile::ReadOnly) | QIODevice::Text)
        {
    
        model->setHorizontalHeaderLabels(QStringList() << "Date/Time" << "PowerConsumed (W)");
    
        int lineindex = 0;
        QTextStream flux(&file);
    
         flux.readLineInto(nullptr); // Passe la 1ère ligne
    
        while(!flux.atEnd())
        {
            QString ligne = flux.readLine();
            QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
    
            for(int j=0;j < champs.size();j++)
            {
                QString value = champs.at(j);
                QStandardItem *item = new QStandardItem(value);
                model->setItem(lineindex, j, item);
            }
            lineindex++;
        }
    
        file.close();
    
            ui->tableView->setModel(model);
        }
    }
    

    Result:

    31ad259f-b99b-4a51-a8f2-459cbbea5b0a-image.png

    Now my goal is to recover only the first two columns

    R Offline
    R Offline
    Raphawel
    wrote on last edited by Raphawel
    #16

    @Raphawel To recover the first two colums here is the program:

    void MainWindow::LireFichierCSV()
    {
    
        QStandardItemModel *model= new QStandardItemModel();
        //QFile file("test.csv");
    
        QStringList location = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);  // Viens lire tout les fichiers du répertoire Document, mettre ::DesktopLocation pour le bureau
        QString result = location[0];
        result = result + QString("/system_meter_conso.csv");
        QFile file(result);
    
        if(file.open(QFile::ReadOnly) | QIODevice::Text)
        {
    
        model->setHorizontalHeaderLabels(QStringList() << "Date/Time" << "PowerConsumed (W)");
    
        int lineindex = 0;
        QTextStream flux(&file);
    
    
    
         flux.readLineInto(nullptr); // Passe la 1ère ligne
    
         QStringList lineList = {};
         QStringList columnList = {};
    
    
    
        while(!flux.atEnd())
        {
               QString ligne = flux.readLine();
               QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
    
               lineList.append(champs[0]);
               columnList.append(champs[1]);
    
    
                QString valueL = lineList[lineindex];
                QString valueC = columnList[lineindex];
                QStandardItem *itemL = new QStandardItem(valueL);
                QStandardItem *itemC = new QStandardItem(valueC);
                model->setItem(lineindex, 0, itemL );
                model->setItem(lineindex, 1,  itemC);
               lineindex++;
    
            /*for(int j=0;j < champs.size();j++)
            {
                QString value = champs.at(j);
                QStandardItem *item = new QStandardItem(value);
                model->setItem(lineindex, j, item);
            }
            lineindex++;*/
        }
    
        file.close();
    
            ui->tableView->setModel(model);
        }
    
    }
    

    Result:
    576a0f0f-b4ed-4862-882c-7de650563d44-image.png

    R 1 Reply Last reply
    0
    • R Raphawel

      @Raphawel To recover the first two colums here is the program:

      void MainWindow::LireFichierCSV()
      {
      
          QStandardItemModel *model= new QStandardItemModel();
          //QFile file("test.csv");
      
          QStringList location = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);  // Viens lire tout les fichiers du répertoire Document, mettre ::DesktopLocation pour le bureau
          QString result = location[0];
          result = result + QString("/system_meter_conso.csv");
          QFile file(result);
      
          if(file.open(QFile::ReadOnly) | QIODevice::Text)
          {
      
          model->setHorizontalHeaderLabels(QStringList() << "Date/Time" << "PowerConsumed (W)");
      
          int lineindex = 0;
          QTextStream flux(&file);
      
      
      
           flux.readLineInto(nullptr); // Passe la 1ère ligne
      
           QStringList lineList = {};
           QStringList columnList = {};
      
      
      
          while(!flux.atEnd())
          {
                 QString ligne = flux.readLine();
                 QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
      
                 lineList.append(champs[0]);
                 columnList.append(champs[1]);
      
      
                  QString valueL = lineList[lineindex];
                  QString valueC = columnList[lineindex];
                  QStandardItem *itemL = new QStandardItem(valueL);
                  QStandardItem *itemC = new QStandardItem(valueC);
                  model->setItem(lineindex, 0, itemL );
                  model->setItem(lineindex, 1,  itemC);
                 lineindex++;
      
              /*for(int j=0;j < champs.size();j++)
              {
                  QString value = champs.at(j);
                  QStandardItem *item = new QStandardItem(value);
                  model->setItem(lineindex, j, item);
              }
              lineindex++;*/
          }
      
          file.close();
      
              ui->tableView->setModel(model);
          }
      
      }
      

      Result:
      576a0f0f-b4ed-4862-882c-7de650563d44-image.png

      R Offline
      R Offline
      Raphawel
      wrote on last edited by Raphawel
      #17

      Could someone help me please ? :(

      void GraphConso::LireFichierCSV()
      {
          QStandardItemModel *model= new QStandardItemModel();
          //QFile file("test.csv");
      
          QStringList location = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);  // Viens lire tout les fichiers du répertoire Document, mettre ::DesktopLocation pour le bureau
          QString result = location[0];
          result = result + QString("/system_meter_conso.csv");
          QFile file(result);
      
          if(file.open(QFile::ReadOnly) | QIODevice::Text)
          {
      
              model->setHorizontalHeaderLabels(QStringList() << "Date/Time" << "PowerConsumed (W)");
      
              int lineindex = 0;
              QTextStream flux(&file);
      
      
      
              flux.readLineInto(nullptr); // Passe la 1ère ligne
      
              QStringList lineList = {};
              QStringList columnList = {};
      
      
      
              while(!flux.atEnd())
              {
                  QString ligne = flux.readLine();
                  QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
      
                  lineList.append(champs[0]);
                  columnList.append(champs[1]);
                  ui->customplot->graph(0)->setData(lineList, columnList);
                  ui->customplot->replot();
      
      
                  QString valueL = lineList[lineindex];
                  QString valueC = columnList[lineindex];
                  QStandardItem *itemL = new QStandardItem(valueL);
                  QStandardItem *itemC = new QStandardItem(valueC);
                  model->setItem(lineindex, 0,  itemL);
                  model->setItem(lineindex, 1,  itemC);
      
                  lineindex++;
      
              }
      
              file.close();
      
              ui->tableView->setModel(model);
      
          }
      
      }
      

      I would like to display on my graph, the values of the two columns with x -> Date/Time and y -> PowerConsumed.

      Here I have used the rows :

      ui->customplot->graph(0)->QCPGraph::setData(lineList, columnList);
                 ui->customplot->replot();
      

      I still don't know if this technique works but I get this as an error:
      Can you help me please ?

      C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:122: erreur : 'QCPGraph' is not a base of 'QCustomPlot'
                   ui->customplot->QCPGraph::setData(lineList, columnList);
      

      I don't know what this means

      JonBJ 1 Reply Last reply
      0
      • R Raphawel

        Could someone help me please ? :(

        void GraphConso::LireFichierCSV()
        {
            QStandardItemModel *model= new QStandardItemModel();
            //QFile file("test.csv");
        
            QStringList location = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);  // Viens lire tout les fichiers du répertoire Document, mettre ::DesktopLocation pour le bureau
            QString result = location[0];
            result = result + QString("/system_meter_conso.csv");
            QFile file(result);
        
            if(file.open(QFile::ReadOnly) | QIODevice::Text)
            {
        
                model->setHorizontalHeaderLabels(QStringList() << "Date/Time" << "PowerConsumed (W)");
        
                int lineindex = 0;
                QTextStream flux(&file);
        
        
        
                flux.readLineInto(nullptr); // Passe la 1ère ligne
        
                QStringList lineList = {};
                QStringList columnList = {};
        
        
        
                while(!flux.atEnd())
                {
                    QString ligne = flux.readLine();
                    QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
        
                    lineList.append(champs[0]);
                    columnList.append(champs[1]);
                    ui->customplot->graph(0)->setData(lineList, columnList);
                    ui->customplot->replot();
        
        
                    QString valueL = lineList[lineindex];
                    QString valueC = columnList[lineindex];
                    QStandardItem *itemL = new QStandardItem(valueL);
                    QStandardItem *itemC = new QStandardItem(valueC);
                    model->setItem(lineindex, 0,  itemL);
                    model->setItem(lineindex, 1,  itemC);
        
                    lineindex++;
        
                }
        
                file.close();
        
                ui->tableView->setModel(model);
        
            }
        
        }
        

        I would like to display on my graph, the values of the two columns with x -> Date/Time and y -> PowerConsumed.

        Here I have used the rows :

        ui->customplot->graph(0)->QCPGraph::setData(lineList, columnList);
                   ui->customplot->replot();
        

        I still don't know if this technique works but I get this as an error:
        Can you help me please ?

        C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:122: erreur : 'QCPGraph' is not a base of 'QCustomPlot'
                     ui->customplot->QCPGraph::setData(lineList, columnList);
        

        I don't know what this means

        JonBJ Offline
        JonBJ Offline
        JonB
        wrote on last edited by
        #18

        @Raphawel
        Your code shows

        ui->customplot->graph(0)->QCPGraph::setData
        

        but the error message shows

        ui->customplot->QCPGraph::setData
        

        so which do you actually have? Do you/are you supposed to have a QCPGraph object you are trying to call setData() on? I don't even know what your "if this technique works" refers to.

        R 1 Reply Last reply
        0
        • JonBJ JonB

          @Raphawel
          Your code shows

          ui->customplot->graph(0)->QCPGraph::setData
          

          but the error message shows

          ui->customplot->QCPGraph::setData
          

          so which do you actually have? Do you/are you supposed to have a QCPGraph object you are trying to call setData() on? I don't even know what your "if this technique works" refers to.

          R Offline
          R Offline
          Raphawel
          wrote on last edited by
          #19

          @JonB Ohh sorry, the real mistake is this:

          With the line :

          lineList.append(champs[0]);
                      columnList.append(champs[1]);
          
                      //QVector<const char*> xData2 = lineList;
                      //QVector<const char*> yData2 = columnList;
                      ui->customplot->graph(0)->setData(lineList, columnList);
                      ui->customplot->replot();
          

          And the error :

          C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: erreur : no matching function for call to 'QCPGraph::setData(QStringList&, QStringList&)'
                       ui->customplot->graph(0)->setData(lineList, columnList);
                                                                             ^
          

          My IDE :
          6a93f9fc-ae33-4f74-a0f8-aa6b7ecc90da-image.png

          When I say if this technique works, I mean using:

          ui->customplot->graph(0)->setData(lineList, columnList);
          

          To display on the graph (custom plot object) the points from my csv file

          jsulmJ JonBJ 2 Replies Last reply
          0
          • R Raphawel

            @JonB Ohh sorry, the real mistake is this:

            With the line :

            lineList.append(champs[0]);
                        columnList.append(champs[1]);
            
                        //QVector<const char*> xData2 = lineList;
                        //QVector<const char*> yData2 = columnList;
                        ui->customplot->graph(0)->setData(lineList, columnList);
                        ui->customplot->replot();
            

            And the error :

            C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: erreur : no matching function for call to 'QCPGraph::setData(QStringList&, QStringList&)'
                         ui->customplot->graph(0)->setData(lineList, columnList);
                                                                               ^
            

            My IDE :
            6a93f9fc-ae33-4f74-a0f8-aa6b7ecc90da-image.png

            When I say if this technique works, I mean using:

            ui->customplot->graph(0)->setData(lineList, columnList);
            

            To display on the graph (custom plot object) the points from my csv file

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #20

            @Raphawel The error message is very clear.
            Please check documentation what parameters QCPGraph::setData expects (https://www.qcustomplot.com/documentation/classQCPGraph.html#a73578d786532132310a926c3cd529b29).

            https://forum.qt.io/topic/113070/qt-code-of-conduct

            R 1 Reply Last reply
            1
            • R Raphawel

              @JonB Ohh sorry, the real mistake is this:

              With the line :

              lineList.append(champs[0]);
                          columnList.append(champs[1]);
              
                          //QVector<const char*> xData2 = lineList;
                          //QVector<const char*> yData2 = columnList;
                          ui->customplot->graph(0)->setData(lineList, columnList);
                          ui->customplot->replot();
              

              And the error :

              C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: erreur : no matching function for call to 'QCPGraph::setData(QStringList&, QStringList&)'
                           ui->customplot->graph(0)->setData(lineList, columnList);
                                                                                 ^
              

              My IDE :
              6a93f9fc-ae33-4f74-a0f8-aa6b7ecc90da-image.png

              When I say if this technique works, I mean using:

              ui->customplot->graph(0)->setData(lineList, columnList);
              

              To display on the graph (custom plot object) the points from my csv file

              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by
              #21

              @Raphawel
              OK, so although you have not said I guess ui->customplot->graph(0) must be a QCPGraph?

              Given the error message tells you what the issue is I don't know what further to say. You are passing QCPGraph::setData() two QStringLists, list of strings, and not surprisingly it does not accept those. So look at QCPGraph::setData() documentation to see what it does accept.

              1 Reply Last reply
              0
              • jsulmJ jsulm

                @Raphawel The error message is very clear.
                Please check documentation what parameters QCPGraph::setData expects (https://www.qcustomplot.com/documentation/classQCPGraph.html#a73578d786532132310a926c3cd529b29).

                R Offline
                R Offline
                Raphawel
                wrote on last edited by
                #22

                @jsulm Yes the message tells me that I need QVectors inside setData() :

                void QCPGraph::setData ( const QVector< double > &  keys, const QVector< double > &  values, bool  alreadySorted = false  )
                

                So I readapted:

                lineList.append(champs[0]);
                            columnList.append(champs[1]);
                
                            QVector<double> xData2 = lineList;
                            QVector<double> yData2 = columnList;
                            ui->customplot->graph(0)->setData(xData2, yData2);
                            ui->customplot->replot();
                

                But I still have errors due to a conversion problem:

                C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:123: erreur : conversion from 'QStringList' to non-scalar type 'QVector<double>' requested
                             QVector<double> xData2 = lineList;
                                                      ^
                
                C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:124: erreur : conversion from 'QStringList' to non-scalar type 'QVector<double>' requested
                             QVector<double> yData2 = columnList;
                                                      ^
                

                I'm sorry if the errors are really glaring but I really don't see how to solve them

                S 1 Reply Last reply
                0
                • R Raphawel

                  @jsulm Yes the message tells me that I need QVectors inside setData() :

                  void QCPGraph::setData ( const QVector< double > &  keys, const QVector< double > &  values, bool  alreadySorted = false  )
                  

                  So I readapted:

                  lineList.append(champs[0]);
                              columnList.append(champs[1]);
                  
                              QVector<double> xData2 = lineList;
                              QVector<double> yData2 = columnList;
                              ui->customplot->graph(0)->setData(xData2, yData2);
                              ui->customplot->replot();
                  

                  But I still have errors due to a conversion problem:

                  C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:123: erreur : conversion from 'QStringList' to non-scalar type 'QVector<double>' requested
                               QVector<double> xData2 = lineList;
                                                        ^
                  
                  C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:124: erreur : conversion from 'QStringList' to non-scalar type 'QVector<double>' requested
                               QVector<double> yData2 = columnList;
                                                        ^
                  

                  I'm sorry if the errors are really glaring but I really don't see how to solve them

                  S Offline
                  S Offline
                  SimonSchroeder
                  wrote on last edited by
                  #23

                  @Raphawel You need to transform all entries inside the lists individually. For example, you could use lineList[0].toDouble() to convert a single QString to a double value. There is not automatic conversion from strings to numbers. In imperative programming a for loop comes to mind. However, here is a more functional style approach to "copy" the data over using standard C++:

                  QVector<double> xData2;
                  std::transform(lineList.begin(), lineList.end(), std::back_inserter(xData2), [](const QString &str) { return str.toDouble(); });
                  
                  R 1 Reply Last reply
                  1
                  • S SimonSchroeder

                    @Raphawel You need to transform all entries inside the lists individually. For example, you could use lineList[0].toDouble() to convert a single QString to a double value. There is not automatic conversion from strings to numbers. In imperative programming a for loop comes to mind. However, here is a more functional style approach to "copy" the data over using standard C++:

                    QVector<double> xData2;
                    std::transform(lineList.begin(), lineList.end(), std::back_inserter(xData2), [](const QString &str) { return str.toDouble(); });
                    
                    R Offline
                    R Offline
                    Raphawel
                    wrote on last edited by
                    #24

                    @SimonSchroeder

                            QStringList lineList = {};
                            QStringList columnList = {};
                            QVector<double> xData2;
                            QVector<double> yData2;
                    
                            while(!flux.atEnd())
                            {
                                QString ligne = flux.readLine();
                                QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                    
                                lineList.append(champs[0]);
                                columnList.append(champs[1]);
                    
                                xData2.append(champs[0].toDouble());
                                yData2.append(champs[1].toDouble());
                                
                                ui->customplot->graph(0)->setData(xData2, yData2);
                                ui->customplot->replot();
                    

                    I tried to do a QString to double conversion my way. And the program compiles well. And I have the impression that it did the conversion well. Except that I have an error that appears after compilation :

                    16a94e6f-12bd-4aab-8ab6-e264b3eb2e8f-image.png

                    Already if the help you gave me doesn't correspond at all to what I just did, can you tell me please ?

                    And what does this message mean : The inferior stopped because it received a signal from the operating system

                    jsulmJ JonBJ 2 Replies Last reply
                    0
                    • R Raphawel

                      @SimonSchroeder

                              QStringList lineList = {};
                              QStringList columnList = {};
                              QVector<double> xData2;
                              QVector<double> yData2;
                      
                              while(!flux.atEnd())
                              {
                                  QString ligne = flux.readLine();
                                  QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                      
                                  lineList.append(champs[0]);
                                  columnList.append(champs[1]);
                      
                                  xData2.append(champs[0].toDouble());
                                  yData2.append(champs[1].toDouble());
                                  
                                  ui->customplot->graph(0)->setData(xData2, yData2);
                                  ui->customplot->replot();
                      

                      I tried to do a QString to double conversion my way. And the program compiles well. And I have the impression that it did the conversion well. Except that I have an error that appears after compilation :

                      16a94e6f-12bd-4aab-8ab6-e264b3eb2e8f-image.png

                      Already if the help you gave me doesn't correspond at all to what I just did, can you tell me please ?

                      And what does this message mean : The inferior stopped because it received a signal from the operating system

                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #25

                      @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                      lineList.append(champs[0]);
                      columnList.append(champs[1]);

                      You're not checking how many elements the list actually contains!
                      Also, take a look at the stack trace: it tells where in your code it crashes.

                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                      1 Reply Last reply
                      2
                      • R Raphawel

                        @SimonSchroeder

                                QStringList lineList = {};
                                QStringList columnList = {};
                                QVector<double> xData2;
                                QVector<double> yData2;
                        
                                while(!flux.atEnd())
                                {
                                    QString ligne = flux.readLine();
                                    QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                        
                                    lineList.append(champs[0]);
                                    columnList.append(champs[1]);
                        
                                    xData2.append(champs[0].toDouble());
                                    yData2.append(champs[1].toDouble());
                                    
                                    ui->customplot->graph(0)->setData(xData2, yData2);
                                    ui->customplot->replot();
                        

                        I tried to do a QString to double conversion my way. And the program compiles well. And I have the impression that it did the conversion well. Except that I have an error that appears after compilation :

                        16a94e6f-12bd-4aab-8ab6-e264b3eb2e8f-image.png

                        Already if the help you gave me doesn't correspond at all to what I just did, can you tell me please ?

                        And what does this message mean : The inferior stopped because it received a signal from the operating system

                        JonBJ Offline
                        JonBJ Offline
                        JonB
                        wrote on last edited by JonB
                        #26

                        @Raphawel

                        1. Make sure that the ligne.split() always returns (at least) 2 elements.
                        2. Check the result from champs[0].toDouble() (hint: it takes an optional bool *ok = nullptr parameter). Since I see your column #0 seems to contain date string how do you expect them to convert to a double?
                        3. I don't think this is required, but does it make any difference if you make x/yData2 vectors have lifetime scope outside the code you show, e.g. as class member variables? [Having said that I suspect the setData(xData2, yData2) takes a copy anyway?
                        4. Make sure your graph(0) does point to a valid QCPGraph and that starts out empty.
                        5. Try a clearData() before calling setData() each time.

                        The first thing to check is #2 (and of course #1).

                        R 1 Reply Last reply
                        1
                        • JonBJ JonB

                          @Raphawel

                          1. Make sure that the ligne.split() always returns (at least) 2 elements.
                          2. Check the result from champs[0].toDouble() (hint: it takes an optional bool *ok = nullptr parameter). Since I see your column #0 seems to contain date string how do you expect them to convert to a double?
                          3. I don't think this is required, but does it make any difference if you make x/yData2 vectors have lifetime scope outside the code you show, e.g. as class member variables? [Having said that I suspect the setData(xData2, yData2) takes a copy anyway?
                          4. Make sure your graph(0) does point to a valid QCPGraph and that starts out empty.
                          5. Try a clearData() before calling setData() each time.

                          The first thing to check is #2 (and of course #1).

                          R Offline
                          R Offline
                          Raphawel
                          wrote on last edited by Raphawel
                          #27

                          @JonB Thank you very much for detailing the steps to follow :) Considering my level, I tried to reproduce what is asked:

                          1. For lineindex = 0 :

                          QStringList champs = ligne.split(";", QString::KeepEmptyParts); return 4 éléments :
                          champs[0] = "09/21/2022 02:30 PM CEST"
                          champs[1] = ""
                          champs[2] = ""
                          champs[3] = "576"

                          1. For lineindex = 0 :
                            lineList.append(champs[0]); -> return "09/21/2022 02:30 ..." -> type QString
                            columnList.append(champs[1]); -> return "" -> type QString
                            xData2.append(champs[0].toDouble()); -> return "0" -> type double
                            yData2.append(champs[1].toDouble()); -> return "0" - > type double

                            xData2 and yData2-> Type QVector <double>

                          For lineindex = 1 :
                          lineList.append(champs[0]); -> return "09/21/2022 02:45 ..." -> type QString
                          columnList.append(champs[1]); -> return "2.712" -> type QString
                          xData2.append(champs[0].toDouble()); -> return "0" -> type double
                          yData2.append(champs[1].toDouble()); -> return "0" - > type double

                          cda8e963-2cd1-4313-9e6c-eff99e5c4bd3-image.png

                          But I see that yData2 doesn't understand float values when it is a double when for example :

                          columnlist[1] = 2.712 then yData2[1] = 0

                          But that it understands the integer values:

                          columnlist[3] = 240 then yData[3] = 240.

                          On the other hand, I have to find a way to do the conversion of a QString for xData

                          1. It does not change anything

                          2. I am blind, I forgot to add :

                          ui->customplot->addGraph();
                          
                          1. I added it

                          So, this time I removed this error : https://forum.qt.io/post/749704 as I can access my graph.

                          jsulmJ 1 Reply Last reply
                          0
                          • R Raphawel

                            @JonB Thank you very much for detailing the steps to follow :) Considering my level, I tried to reproduce what is asked:

                            1. For lineindex = 0 :

                            QStringList champs = ligne.split(";", QString::KeepEmptyParts); return 4 éléments :
                            champs[0] = "09/21/2022 02:30 PM CEST"
                            champs[1] = ""
                            champs[2] = ""
                            champs[3] = "576"

                            1. For lineindex = 0 :
                              lineList.append(champs[0]); -> return "09/21/2022 02:30 ..." -> type QString
                              columnList.append(champs[1]); -> return "" -> type QString
                              xData2.append(champs[0].toDouble()); -> return "0" -> type double
                              yData2.append(champs[1].toDouble()); -> return "0" - > type double

                              xData2 and yData2-> Type QVector <double>

                            For lineindex = 1 :
                            lineList.append(champs[0]); -> return "09/21/2022 02:45 ..." -> type QString
                            columnList.append(champs[1]); -> return "2.712" -> type QString
                            xData2.append(champs[0].toDouble()); -> return "0" -> type double
                            yData2.append(champs[1].toDouble()); -> return "0" - > type double

                            cda8e963-2cd1-4313-9e6c-eff99e5c4bd3-image.png

                            But I see that yData2 doesn't understand float values when it is a double when for example :

                            columnlist[1] = 2.712 then yData2[1] = 0

                            But that it understands the integer values:

                            columnlist[3] = 240 then yData[3] = 240.

                            On the other hand, I have to find a way to do the conversion of a QString for xData

                            1. It does not change anything

                            2. I am blind, I forgot to add :

                            ui->customplot->addGraph();
                            
                            1. I added it

                            So, this time I removed this error : https://forum.qt.io/post/749704 as I can access my graph.

                            jsulmJ Offline
                            jsulmJ Offline
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by
                            #28

                            @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                            lineList.append(champs[0]); -> return "09/21/2022 02:30 ..." -> type QString
                            columnList.append(champs[1]); -> return "" -> type QString
                            xData2.append(champs[0].toDouble()); -> return "0" -> type double
                            yData2.append(champs[1].toDouble()); -> return "0" - > type double

                            Neither "09/21/2022 02:30 ..." nor "" empty string can be converted to a double...

                            https://forum.qt.io/topic/113070/qt-code-of-conduct

                            1 Reply Last reply
                            1
                            • S Offline
                              S Offline
                              SimonSchroeder
                              wrote on last edited by
                              #29

                              Most likely the reason for your crash is that there is an extra empty line at the end of the file. You are trying to convert that as well. Hence why you need to check if there are enough items.

                              It is not surprising that a date cannot be converted to a double. Does QCustomPlot support dates? Otherwise you need to use QDateTime to convert the string to a date and use one of its functions to convert it to milliseconds from a specific date (most likely the first date you have) and assign the milliseconds to the double vector (maybe convert them to days instead).

                              Concerning the second column: Do you get numbers like 2.712 or 2,712? Which is the string you read from the .csv file? The screenshot is telling a different story than your text. Most likely this is related to the locale that is used.

                              1 Reply Last reply
                              1
                              • R Offline
                                R Offline
                                Raphawel
                                wrote on last edited by Raphawel
                                #30

                                @SimonSchroeder The string I changed the number of lines to look at (30).
                                So the values of the 1st column are only in the form: "MM/dd/yyyy hh:mm AP".

                                The string I get back is : "MM/dd/yyyy hh:mm AP" for lineList

                                For xData2:
                                Before my while it is defined as a

                                QVector<double> xData2;
                                

                                In the while I convert it with

                                xData2.append(QDateTime::fromString(fields[0], "hh:mm").toTime_t())
                                

                                I understood that we can't convert a string to a double but the problem is that setData only accepts QVector<double>, why ???

                                And whatever the type I put (not double) I have all the time the same errors

                                C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:140: error : no matching function for call to 'QCPGraph::setData(QVector<char>&, QVector<double>&)'
                                         ui->customplot->graph(0)->setData(xData2, yData2);
                                                                                         ^
                                

                                My questions: is there a simple way to display a string like mine "MM/dd/yyyy hh:mm AP" on the x axis and an integer(power) on the Y axis.

                                So by having : setData(QString, double). Despite the fact that setData doesn't accept anything aside doubles

                                So the conversion method you just proposed @SimonSChroeder. I tried to do it:
                                ```
                                QStringList lineList = {};
                                QStringList columnList = {};
                                QVector<double> xData2;
                                QVector<double> yData2;
                                QDateTime referenceDateTime;

                                    while(lineindex<30)
                                    {
                                        QString ligne = flux.readLine();
                                        QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                                
                                
                                        lineList.append(champs[0]);
                                        columnList.append(champs[1]);
                                
                                        if(lineindex==0)
                                        {
                                            referenceDateTime = QDateTime::fromString(lineList,"MM/dd/yyyy hh:mm AP");
                                        }
                                
                                        QDateTime dateTime = QDateTime::fromString(champs[0],"MM/dd/yyyy hh:mm AP");
                                
                                        qint64 milliseconds = dateTime.toMSecsSinceEpoch() - referenceDateTime.toMSecsSinceEpoch();
                                        xData2.append(milliseconds); // "MM/dd/yyyy hh:mm AP"
                                        yData2.append(champs[1].toDouble());
                                
                                        QString valueL = lineList[lineindex];
                                        QString valueC = columnList[lineindex];
                                        QStandardItem *itemL = new QStandardItem(valueL);
                                        QStandardItem *itemC = new QStandardItem(valueC);
                                        model->setItem(lineindex, 0,  itemL);
                                        model->setItem(lineindex, 1,  itemC);
                                
                                        lineindex++;
                                
                                    }
                                
                                    file.close();
                                
                                    ui->customplot->addGraph();
                                    ui->customplot->graph(0)->data()->clear();
                                    ui->customplot->graph(0)->setData(xData2, yData2);
                                

                                But it doesn't work because of the same problem:

                                C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: error : no matching function for call to 'QDateTime::fromString(QStringList&, const char [20])'
                                                 referenceDateTime = QDateTime::fromString(lineList, "MM/dd/yyyy hh:mm AP");
                                                                                                                         ^
                                

                                "Do you get numbers like 2.712 or 2,712?" For the 2nd column, I get values 2,712

                                jsulmJ S 2 Replies Last reply
                                0
                                • R Raphawel

                                  @SimonSchroeder The string I changed the number of lines to look at (30).
                                  So the values of the 1st column are only in the form: "MM/dd/yyyy hh:mm AP".

                                  The string I get back is : "MM/dd/yyyy hh:mm AP" for lineList

                                  For xData2:
                                  Before my while it is defined as a

                                  QVector<double> xData2;
                                  

                                  In the while I convert it with

                                  xData2.append(QDateTime::fromString(fields[0], "hh:mm").toTime_t())
                                  

                                  I understood that we can't convert a string to a double but the problem is that setData only accepts QVector<double>, why ???

                                  And whatever the type I put (not double) I have all the time the same errors

                                  C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:140: error : no matching function for call to 'QCPGraph::setData(QVector<char>&, QVector<double>&)'
                                           ui->customplot->graph(0)->setData(xData2, yData2);
                                                                                           ^
                                  

                                  My questions: is there a simple way to display a string like mine "MM/dd/yyyy hh:mm AP" on the x axis and an integer(power) on the Y axis.

                                  So by having : setData(QString, double). Despite the fact that setData doesn't accept anything aside doubles

                                  So the conversion method you just proposed @SimonSChroeder. I tried to do it:
                                  ```
                                  QStringList lineList = {};
                                  QStringList columnList = {};
                                  QVector<double> xData2;
                                  QVector<double> yData2;
                                  QDateTime referenceDateTime;

                                      while(lineindex<30)
                                      {
                                          QString ligne = flux.readLine();
                                          QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                                  
                                  
                                          lineList.append(champs[0]);
                                          columnList.append(champs[1]);
                                  
                                          if(lineindex==0)
                                          {
                                              referenceDateTime = QDateTime::fromString(lineList,"MM/dd/yyyy hh:mm AP");
                                          }
                                  
                                          QDateTime dateTime = QDateTime::fromString(champs[0],"MM/dd/yyyy hh:mm AP");
                                  
                                          qint64 milliseconds = dateTime.toMSecsSinceEpoch() - referenceDateTime.toMSecsSinceEpoch();
                                          xData2.append(milliseconds); // "MM/dd/yyyy hh:mm AP"
                                          yData2.append(champs[1].toDouble());
                                  
                                          QString valueL = lineList[lineindex];
                                          QString valueC = columnList[lineindex];
                                          QStandardItem *itemL = new QStandardItem(valueL);
                                          QStandardItem *itemC = new QStandardItem(valueC);
                                          model->setItem(lineindex, 0,  itemL);
                                          model->setItem(lineindex, 1,  itemC);
                                  
                                          lineindex++;
                                  
                                      }
                                  
                                      file.close();
                                  
                                      ui->customplot->addGraph();
                                      ui->customplot->graph(0)->data()->clear();
                                      ui->customplot->graph(0)->setData(xData2, yData2);
                                  

                                  But it doesn't work because of the same problem:

                                  C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: error : no matching function for call to 'QDateTime::fromString(QStringList&, const char [20])'
                                                   referenceDateTime = QDateTime::fromString(lineList, "MM/dd/yyyy hh:mm AP");
                                                                                                                           ^
                                  

                                  "Do you get numbers like 2.712 or 2,712?" For the 2nd column, I get values 2,712

                                  jsulmJ Offline
                                  jsulmJ Offline
                                  jsulm
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #31

                                  @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                  setData only accepts QVector<double>, why ???

                                  Because it plots vectors of doubles.

                                  "I understood that we can't convert a string to a double" - this is wrong. You can convert a string to double if the string contains valid text representation of a number.
                                  ""09/21/2022 02:30" - this is NOT a double!

                                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  R 1 Reply Last reply
                                  0
                                  • jsulmJ jsulm

                                    @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                    setData only accepts QVector<double>, why ???

                                    Because it plots vectors of doubles.

                                    "I understood that we can't convert a string to a double" - this is wrong. You can convert a string to double if the string contains valid text representation of a number.
                                    ""09/21/2022 02:30" - this is NOT a double!

                                    R Offline
                                    R Offline
                                    Raphawel
                                    wrote on last edited by Raphawel
                                    #32

                                    @jsulm said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                    Because it plots vectors of doubles.
                                    "I understood that we can't convert a string to a double" - this is wrong. You can convert a string to double if the string contains valid text representation of a number.
                                    ""09/21/2022 02:30" - this is NOT a double!

                                    "09/21/2022 02:30" I get that. So I have to convert it using @SimonSChroeder's method to hope to display it.
                                    Why is it not as easy as in Excel to display the x axis with dates like this....

                                    And also aren't there vector plots of QString?

                                    jsulmJ 1 Reply Last reply
                                    0
                                    • R Raphawel

                                      @jsulm said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                      Because it plots vectors of doubles.
                                      "I understood that we can't convert a string to a double" - this is wrong. You can convert a string to double if the string contains valid text representation of a number.
                                      ""09/21/2022 02:30" - this is NOT a double!

                                      "09/21/2022 02:30" I get that. So I have to convert it using @SimonSChroeder's method to hope to display it.
                                      Why is it not as easy as in Excel to display the x axis with dates like this....

                                      And also aren't there vector plots of QString?

                                      jsulmJ Offline
                                      jsulmJ Offline
                                      jsulm
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #33

                                      @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                      And also aren't there vector plots of QString?

                                      Why don't you read QCustomPlot documentation? It is not part of Qt.
                                      So, if you read their documentation you will find this: https://www.qcustomplot.com/index.php/tutorials/basicplotting scroll down to "Plotting date and time data"...

                                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                                      1 Reply Last reply
                                      2
                                      • R Raphawel

                                        @SimonSchroeder The string I changed the number of lines to look at (30).
                                        So the values of the 1st column are only in the form: "MM/dd/yyyy hh:mm AP".

                                        The string I get back is : "MM/dd/yyyy hh:mm AP" for lineList

                                        For xData2:
                                        Before my while it is defined as a

                                        QVector<double> xData2;
                                        

                                        In the while I convert it with

                                        xData2.append(QDateTime::fromString(fields[0], "hh:mm").toTime_t())
                                        

                                        I understood that we can't convert a string to a double but the problem is that setData only accepts QVector<double>, why ???

                                        And whatever the type I put (not double) I have all the time the same errors

                                        C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:140: error : no matching function for call to 'QCPGraph::setData(QVector<char>&, QVector<double>&)'
                                                 ui->customplot->graph(0)->setData(xData2, yData2);
                                                                                                 ^
                                        

                                        My questions: is there a simple way to display a string like mine "MM/dd/yyyy hh:mm AP" on the x axis and an integer(power) on the Y axis.

                                        So by having : setData(QString, double). Despite the fact that setData doesn't accept anything aside doubles

                                        So the conversion method you just proposed @SimonSChroeder. I tried to do it:
                                        ```
                                        QStringList lineList = {};
                                        QStringList columnList = {};
                                        QVector<double> xData2;
                                        QVector<double> yData2;
                                        QDateTime referenceDateTime;

                                            while(lineindex<30)
                                            {
                                                QString ligne = flux.readLine();
                                                QStringList champs = ligne.split(";", QString::KeepEmptyParts); //::KeepEmptyParts : Permet de voir les zones vides et de noter les résultats que quand il y en a
                                        
                                        
                                                lineList.append(champs[0]);
                                                columnList.append(champs[1]);
                                        
                                                if(lineindex==0)
                                                {
                                                    referenceDateTime = QDateTime::fromString(lineList,"MM/dd/yyyy hh:mm AP");
                                                }
                                        
                                                QDateTime dateTime = QDateTime::fromString(champs[0],"MM/dd/yyyy hh:mm AP");
                                        
                                                qint64 milliseconds = dateTime.toMSecsSinceEpoch() - referenceDateTime.toMSecsSinceEpoch();
                                                xData2.append(milliseconds); // "MM/dd/yyyy hh:mm AP"
                                                yData2.append(champs[1].toDouble());
                                        
                                                QString valueL = lineList[lineindex];
                                                QString valueC = columnList[lineindex];
                                                QStandardItem *itemL = new QStandardItem(valueL);
                                                QStandardItem *itemC = new QStandardItem(valueC);
                                                model->setItem(lineindex, 0,  itemL);
                                                model->setItem(lineindex, 1,  itemC);
                                        
                                                lineindex++;
                                        
                                            }
                                        
                                            file.close();
                                        
                                            ui->customplot->addGraph();
                                            ui->customplot->graph(0)->data()->clear();
                                            ui->customplot->graph(0)->setData(xData2, yData2);
                                        

                                        But it doesn't work because of the same problem:

                                        C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: error : no matching function for call to 'QDateTime::fromString(QStringList&, const char [20])'
                                                         referenceDateTime = QDateTime::fromString(lineList, "MM/dd/yyyy hh:mm AP");
                                                                                                                                 ^
                                        

                                        "Do you get numbers like 2.712 or 2,712?" For the 2nd column, I get values 2,712

                                        S Offline
                                        S Offline
                                        SimonSchroeder
                                        wrote on last edited by
                                        #34

                                        You need to learn to read error messages more thoroughly.

                                        @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                        C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:140: error : no matching function for call to 'QCPGraph::setData(QVector<char>&, QVector<double>&)'
                                        ui->customplot->graph(0)->setData(xData2, yData2);
                                        This error message tells you that the first parameter you are handing in is of type QVector<char>. By now we have established that it should be QVector<double>. You should be able to figure out that you are passing the wrong variable here.

                                        @Raphawel said in How to retrieve data from an excel .csv file, and put it in a graph with QCustomPlot:

                                        C:\Users\46053500\Documents\Graph_QT\graphConso\graphconso.cpp:125: error : no matching function for call to 'QDateTime::fromString(QStringList&, const char [20])'
                                        referenceDateTime = QDateTime::fromString(lineList, "MM/dd/yyyy hh:mm AP");
                                        And again it tells you that the type of the first parameter is QStringList. As the function name implies it wants a QString instead. So, you need to take one element out of the string list to pass to the function.

                                        Please have a careful look at the error messages because these ones you are posting are really easy to read and see what's wrong. C++ is a strongly typed language. Learn to use this power to your advantage. The compiler exactly tells you when you are using the wrong type. And it is a lot better to have this information at compile time than to have to figure this out at runtime.

                                        1 Reply Last reply
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