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Create a matrix from a .csv file



  • Hi everybody, i'm pretty new to Qt. I've a .csv file with 3 columns : xcoord, ycoord and the value in that position, i try to import it into my qt gui (using a tableView) and now i would like to create a matrix and to show it in the graphicsview. (it is a binary matrix in which i have to activate only the elements of the matrix equal to 1.) i'm searching a way to do this, but i haven't found yet. Does anyone have an idea? I'll be very glad to everybody which helps!


  • Lifetime Qt Champion

    Hi
    So we have a list of x,y,value and you want to draw it as a 2d grid where
    all non zero values should be shown ?

    Im not really sure how/what you want to draw :)

    You could have each x,y be an Item or you could subclass an item and draw it using painter.
    It depends on what we want to do with it.
    If you want to click on "cells" (x,y) then free items is more fun.



  • Yes! but first i have to store it in a matrix or in a 3d array, because now i visualize those data from a csv file into a qtableview but i can't find out how to save into an array. Yes i want to click on cells and save that coordinates. what i have to develop it is sort of map where user can select points (only the available one (equal to 1) and then the code output the coordinates. so free items is better? thank you a lot!


  • Lifetime Qt Champion

    @AliM93
    Hi
    Im not 100% sure what a 3d array would be so maybe i dont understand it fully what data you have.

    I imagine something like

    struct DataRow {
    float x;
    float y;
    int value;
    }

    std::vector<DataRow> Data;

    so just a list of x,y,value.

    We then plot this list to the matching x,y values but we dont store it as a matrix as such.

    But else explain what type of array/3d/matrix you want ?

    You can also do
    int matrix[maxx][maxy];
    So the storage structure is like we want to display it.
    This only works well if the limits of x and y is somewhat reasonable.
    If they have huge gaps etc then such 1:1 mapping can be annoying.

    https://www.tutorialspoint.com/cplusplus/cpp_multi_dimensional_arrays.htm

    Yes if you need to be able to select one or more "cells"/points then free item is more fun as we get selection for free. With painter we must add code to be able to know which "cells" that is selected etc. We get that for free with standalone items.

    How many points are there ?



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  • Lifetime Qt Champion

    @AliM93
    Ok, it really is super straight. The x,y are perfect for

    bool cvsData[14][21];

    You say you want to do it in graphicsview.
    Do you already use this for the app and need zoom and panning and such ? ( or know it well)

    With only 300 points, QPainter is more than fast enough and the coordinate system
    matches the x,y values perfectly.

    But do you need to let the user select ONLY some of the 1 points ?
    We draw all 1 value points to this grid.
    User then has to select some of them or what type of interaction is needed ?

    Im asking to verify that graphicsview is good to approach versus just to make custom QWidget Grid Draw class.



  • No i don''t already use graphicsview.
    Yes, i need to let the user select 3 of 1 points, and i need to save the coordinates of the points selected. I think to create a grid of gray points and to color (for example in green) the 1 points. And yes, the user has to select it clicking on them using the mouse.


  • Lifetime Qt Champion

    @AliM93

    Ok 100 % clear now.

    Well graphicsview/scene are powerfull and awesome but also comes with a quite steep learning curve as
    it has multiple coordinate system and many details.
    On the other hand, it does provide item selection out of the box. ( and much more)
    But you would have to do some reading before being able to create a grid.
    A good starting point could be
    https://doc.qt.io/qt-5/qtwidgets-graphicsview-diagramscene-example.html
    More work but it could handle tons of points and support xoom etc.

    In contrast, a custom widget would have to keep track of selection but actually drawing the grid is just a few
    lines. Since the x,y are so uniform, calculating the point from mouse pos is quite easy.
    Also we just need to override paint event and mouse press and we are there.
    I could write you a rough version in 5 mins. ( provided this is NOT homework :)
    Such widget would not be able to zoom or pan but simply draw a grid that one can click on.

    So Its up to you.
    graphics view is the powerful version but might take some time to dig into.
    A custom Widget using Qpainter and a few functions to select and deselect.
    Since its just 300 points we don't need anything fancy and just redraw the whole gid when something changes.



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  • I think i choose Qpainter. It's not a homework, i would like to do it on my own, but i don't even know how to save data in the bool csvData.
    https://www.tutorialspoint.com/cplusplus/cpp_multi_dimensional_arrays.htm
    i find here some explanation? can you give some hints? thanks


  • Lifetime Qt Champion

    @AliM93
    For this use case, i would also lean towards a custom widget as its quite simply requirements for the grid.
    If you had need zoom or panning, graphicsview.

    Good. Just ask if you run into issues.
    Creator has wizard to make q custom widget quite fast.
    Then you just add PaintEvent and MousePress functions.

    In paint event, you want to use the width/height() to get avialable area.
    That you use to find out the size of each point./cell/grid size.
    so that width()/14
    and Height()/21
    and you then draw each cell or point or what you want.
    You store the size of one cell as a member to use when we click.

    Then in mouse Press.
    When activated we use event->pos() to know where we click with mouse.
    We then use the CellSize we calculated in the paint to find out which cell it must be.
    and then paint it.

    To keep track of this and have the data i would use:

    struct DataPoint {
    int x;
    int y;
    bool value;
    QColor DrawColor; // we change this from selected / not selected.
    bool isSelected: // we set this when we click on it.
    }

    and have that struct in

    DataPoint Data[14][21];

    So we have both data and the color and selection status in one place.

    then we can use it like
    Data[10][10].iSSelected = true; etc
    Data[10][10].DrawColor = Qt:red;

    • but i don't even know how to save data in the bool csvData.
      Well when you read teh file, you get the x,y , right ?
      So you just use them to put value in right place.


  • Yes, i can't understand how to save into the bool csvData the right value. when i read the file i get i table view with 3 columns but i don't know how to read them in a proper manner.


  • Lifetime Qt Champion

    @AliM93 said in Create a matrix from a .csv file:

    Sorry, but when you speak about qcustom widget, you mean that I have to create something from my .ui file? What i should add to show my grid to my .ui file?

    Actually its a complete new Widget that we then put on your main UI form.
    So the new Widget will contain the painting and the data and be standalone from MainWindow.
    Since we do custom painting in the widget, we dont need to give it a UI file as we dont need it here.
    Creator can make most of the code for you. Using the new Wizard.
    Or you can just type it by hand. Its just to subclass QWidget and the virtual functions.

    Yes, i can't understand how to save into the bool csvData the right value. when i read the file i get i table view with 3 columns but i don't know how to read them in a proper manner.

    But it sounds like you do spit each line to x,y, value before adding them, to the model you use for the TableView ?

    Can you show the code ?

    btw: just so you dont think a custom widget is huge work.
    its base is like

    #ifndef GRIDWIDGET_H
    #define GRIDWIDGET_H
    
    #include <QWidget>
    
    class GridWidget : public QWidget
    {
        Q_OBJECT
    public:
        explicit GridWidget(QWidget *parent = nullptr) : QWidget(parent) {}
    protected:
        virtual void paintEvent(QPaintEvent *event) override
        {
        }
        
        virtual void mousePressEvent(QMouseEvent *event) override
        {
        }
    };
    
    #endif // GRIDWIDGET_H
    
    


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  • Lifetime Qt Champion

    @AliM93

    Ah, yes you do split it. so right there you could stuff into the other list too.
    (line 44 first image) line is a StringList and index 0 is x, 1 is y and 2 is value , i assume.

    Actually a custom widget is perfect for use in other project as its just its .cpp and h file and if you include it, you can use it.

    Btw is the TableView and the GridWidget related ?
    it would be possible to reuse the model with your widget if you want to share the data between them but
    its more complicated.



  • No the tableview was just a check for me, but i don't have to use it. i just want to show the data in a grid and that's all.
    i declare it as a QString, is the same of e StringList? yes the order it's like that anyway

    So i have to add a file.h and file.cpp or i can work on this?


  • Lifetime Qt Champion

    @AliM93 said in Create a matrix from a .csv file:

    No the tableview was just a check for me, but i don't have to use it. i just want to show the data in a grid and that's all.
    i declare it as a QString, is the same of e StringList? yes the order it's like that anyway

    Ok, just asking as using a model allows to share data views which is super nice if one needs to be able to edit it and have it reflected at once in some other view. But if you just use it to show data and dont want to edit it. then i would just use
    some small structure to all data needed for the grid display.

    So i have to add a file.h and file.cpp or i can work on this?

    You mean if you can use Matrix class for this custom widget ?
    Yes, but its a QDialog so not perfect fit. ( unless you always want the Grid to popup over the main window)



  • @mrjj from the main_window a open all the other window. and the matrix is a part of another QDialog. now i splith things in order to understand what i have to do but then i have to embed this as a part o QDaialog window. maybe afert a pushbutton clicked i open my grid, the user select and then push another button and i return to my previous GUI with point selected saved.

    So what i have to do now is to add a customgrid.h customgrid.cpp, but what i have to select? to add? if it is not a dialog? a cpp headers and cpp source file separately? or a cpp class?


  • Lifetime Qt Champion

    @AliM93
    Hi
    Well if you want to pop it up anyway, you could leave it as QDialog and draw directly to it but
    could be more handy if it was standalone and you would add it to a QDialog but this is not critical.

    well you just inherit QWidget instead of QDialog and change in cpp where it calls base in constructor.
    xxx) : QDialog(parent) {} -> ) : QWidget(parent) {}

    class GridWidget : public QWidget
    


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  • Lifetime Qt Champion

    @AliM93
    Ah sorry my bad.
    You have an UI file with it and inside that it says its still a QDialog so that what it complains about
    So you must open that UI in text editor and change type ( Creator should be close)
    or remove that it has one.
    That is matrix.h line 23
    and also the setupUI thing and the ui thing line 20

    Its hard to show when you use images for code.

    So do you need UI file ?
    To add other widgets on top of grid ?



  • @mrjj what if i do from new? maybe more clear for me to learn something. and sorry fro the images, up to now i will paste the code.


  • Lifetime Qt Champion

    @AliM93
    Yes lets do a clean widget. I think its good to learn as Creator can really help in this.
    give me 5. ill make some shots.


  • Lifetime Qt Champion

    1:
    alt text
    Choose New file or Project

    2:
    alt text
    Select C++ class

    3:
    Give it a name and set base class to Qwidget
    alt text

    press NEXT, and then next again.

    4:
    we now have the new class and its cpp and .h added to the project
    alt text

    Lets add PaintEvent and MousePress

    Right click the name of the class in the .h file (MatrixWidget)
    and select the Refactor menu and add virtual function
    alt text

    Now type Paint in top
    and check the paintEvent function
    make sure the Insert option is as shown

    alt text

    Dont press OK yet!

    now type Press in top (where you had paint)
    and find the MousePress function and check that.

    Now Press ok.

    Then we are back to the code with our new functions.
    alt text

    Press F4 to switch to cpp file and see it has given you the bodies also.

    alt text

    Now you made your custom widget. ( it might seems a lot first time, but its very fast when used to it :)

    So next part is to add code to paintEvent to draw something.
    We also need your old reader code to get the data and stuff into our structure.


  • Lifetime Qt Champion

    hi
    I hope the above did work for you.
    If yes. Next step is the structure to hold the data.

    
    struct DataPoint {
        int x;
        int y;
        bool value;
        QColor DrawColor; // we change this from selected / not selected.
        bool isSelected; // we set this when we click on it.
    };
    
    const int max_x = 14;
    const int max_y = 21;
    
    class MatrixWidget : public QWidget
    {
        Q_OBJECT
        DataPoint Data[max_x][max_y];  /// this is where we want to load the data to
    public:
        explicit MatrixWidget(QWidget *parent = nullptr);
    
    signals:
    
    
        // QWidget interface
    protected:
        virtual void mousePressEvent(QMouseEvent *event) override;
        virtual void paintEvent(QPaintEvent *event) override;
    };
    


  • sorry ok i put the function


  • Lifetime Qt Champion

    @AliM93
    Thats the Insert Option part
    alt text

    Default its on something else.

    But no worries.

    Do you have them in .h with body also like
    alt text

    If yes, then click on the function name and go to the refactor menu again ( or press alt+enter)
    alt text
    and ask it to move it to .CPP
    do for both functions.



  • @mrjj the code that you wrote me i have to write into .h or .cpp? into the .h i suppose
    we need my previous code to read the data from csv?


  • Lifetime Qt Champion

    @AliM93 said in Create a matrix from a .csv file:

    • the code that you wrote me i have to write into .h or .cpp? into the .h i suppose
      Yes the DataPoint class goes into .h as shown higher up.

    we need my previous code to read the data from csv?

    Yes, this has to be changed to add the values to the
    DataPoint Data[max_x][max_y];
    please post it.



  •   csvModel = new QStandardItemModel(this);
      csvModel->setColumnCount(3);
      csvModel->setHorizontalHeaderLabels(QStringList() <<"x" <<y"" << "bool");
      ui->tableView_1->setModel(csvModel);
      
      QFile file("/home/alice/catkin_ws/src/agree_gui/resources/Punti_tappetino.csv");
      if(!file.open(QFile::ReadOnly | QFile::Text))
      {
        qDebug()<< "FIle not exist";
        
      }
      else {
        QTextStream in(&file);
        while (!in.atEnd())
        {
          QString line = in.readLine();
          QList<QStandardItem *>standardItemsList;
          for(QString item:line.split(";"))
            
        }
        csvModel ->insertRow(csvModel->rowCount(), standardItemsList);
      }
      file.close();
    ```this is in the .cpp file, and in the .h i put 
    

    QStandardItemsModel *csvModel;

    
    
    
    there are also some include in the cpp : 
    

    #include <QTableView>

    #include <iostream>
    #include <fstream>
    #include <sstream>

    
    and om the .h 
    

    #include <QStandardItemModel>


  • Lifetime Qt Champion

    Hi
    Super
    Now we add a new function to our new class.
    lets call it LoadData.

    add these to the .cpp 
    #include <QFile>
    #include <QTextStream>
    #include <QDebug>
    
    // this is changed version of your reader code
    void MatrixWidget::LoadData()
    {
        QFile file("/home/alice/catkin_ws/src/agree_gui/resources/Punti_tappetino.csv");
        if (!file.open(QFile::ReadOnly | QFile::Text)) {
            qDebug() << "FIle not exist";
    
        } else {
            QTextStream in(&file);
            while (!in.atEnd()) {
                QString line = in.readLine();
                QStringList list = line.split(";");
                int x = list.at(0).toInt();
                int y = list.at(1).toInt();
                bool value = list.at(2).toInt();
                if ( x < max_x && y < max_y) // to make sure we dont crash
                    Data[x][y].value = value; // here we store value
                else
                    qDebug() << "x or y bigger than matrix!";
            }
    
        }
        file.close();
    }
    
    

    Do you follow so far ?
    I have not tried this before so not sure how easy its to follow :)



  • @mrjj yes i understand all the flow! super clear, so far.


  • Lifetime Qt Champion

    @AliM93
    Super!
    Could you open Punti_tappetino.csv in textEditor and copy it to say
    https://paste.ofcode.org/
    and give me url ?
    Then i also have some real data to read it to check loaddata works :)



  • @mrjj Done! are you seing it?


  • Lifetime Qt Champion

    @AliM93
    where is the url ?

    you have to press paste it and then copy the adress from the top of browser
    like
    https://paste.ofcode.org/vYJiPZBPqzaDNArjpqPYE7
    (just test)



  • @mrjj https://paste.ofcode.org/XLhSxBmaWcaKj2L9CapQ3s

    sorry my bad

    i have also to declare the function iLoadData in the .h file, right? in the private, protected or in the public slot?


  • Lifetime Qt Champion

    @AliM93
    ah better :)
    yes also add to public section.
    we might call it from outside so its public.



  • @mrjj ok! but i get some trouble with the struct. invalid use of non-static data member.


  • Lifetime Qt Champion

    @AliM93
    can you show line where it says that ´
    Mine compiles fine.



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