how i can identify and read the columns of a csv file ?

[KroMignon]

@julie546 said in how i can identify and read the columns of a csv file ?:

thank you for your answer I was able to solve the problem with
coordXList.append (line.split (','). at (0));
coordYList.append (line.split (','). at (1));

This is a dangerous and no effective way to do!
line.split(',') may return an empty QStringList, so line.split (','). at(0) will crash your application.
And why splitting twice?

I would do it like this:

const auto parts = line.split (',');
if(parts.size() >= 2)
{
    coordXList.append(parts.at(0));
    coordYList.append(parts.at(1));
}

but I would like to put these values ​​in a curve using the Qchart
I tried with
QLineSeries * series = new QLineSeries ();
series-> append (coordXList, coordYList);
but I got an error : no matching membre function for call to append
can you help me please

Have you read QLineSeries::append() documentation??
There is not overload for QLineSeries::append(QStringList, QStringList)!

[KroMignon]

@julie546 said in how i can identify and read the columns of a csv file ?:

so I can't display a graph from a csv file?

Why not?
You have to convert your value to a compatible type. That's all.

[J.Hilk]

@julie546 thats not how programming works.

I assume coordXList and coordYList are string lists ?

than you may, and I emphasise may, get away with:

QLineSeries * series = new QLineSeries ();
for(int i{0}, j{qMin(coordXList.size(), coordYList.size())}; i<j; i++){
      series-> append (coordXList.at(i).toFloat(), coordYList.at(i).toFloat());
}

[julie546]

@J-Hilk yes here is my output ("Y", "0.170138", "0.161089", "0.15901", "0.157898", "0.159706", "0.162481", "0.167204", "0.172876", "0.169802", "0.1677",.....................)
theres an error with series-> append (coordXList.at(i).toFloat(), coordYList.toFloat());
no member named toFloat in QStringList
@KroMignon @J-Hilk can you help me please I am a beginner c ++ I am a student in mechanics but I need qt for my end of study internship

[J.Hilk]

@julie546 said in how i can identify and read the columns of a csv file ?:

no member named toFloat in QStringList

typo on my side, fixed it, but you should be able to fix that as well

[KroMignon]

@julie546 said in how i can identify and read the columns of a csv file ?:

can you help me please I am a beginner c ++ I am a student in mechanics but I need qt for my end of study internship

We have all started as beginner. I have studied electronics, not informatics, so I understand well your problem ;)

The easiest way to create the QLineSeries, is to do it while parsing:

QLineSeries * series = new QLineSeries();
while (!filelidar.atEnd()) {
    QString line = filelidar.readLine();
    const auto parts = line.split (',');
    if(parts.size() >= 2)
    {
        bool ok;
        qreal x = parts.at(0).toFloat(&ok);
        if(!ok)
            continue;
        qreal y = parts.at(1).toFloat(&ok);
        if(!ok)
            continue;
       series->append(x, y);
    }
}

[julie546]

@KroMignon yes it's really difficult to work in a field that you don't study
thank you for your answer I tried like that but I still have an empty curve

if (!filelidar.open(QFile::ReadOnly | QFile::Text) ) {
qDebug() << "File not exists";
} else {

                   QLineSeries * series = new QLineSeries();
                           while (!filelidar.atEnd()) {
                               QString line = filelidar.readLine();
                               const auto parts = line.split (',');
                               if(parts.size() >= 2)
                               {
                                   bool ok;
                                   qreal x = parts.at(0).toFloat(&ok);
                                   if(!ok)
                                       continue;
                                   qreal y = parts.at(1).toFloat(&ok);
                                   if(!ok)
                                       continue;
                                  series->append(x, y);
                               }
                           }



                       QChart *chart = new QChart(); 
                       chart->legend()->hide();
                       chart->addSeries(series);
                       chart->createDefaultAxes();
                       chart->setTitle("Lidar tg15"); 

                       QChartView *chartView = new QChartView(chart);
                       chartView->setRenderHint(QPainter::Antialiasing);

                       QMainWindow window; 
                       window.setCentralWidget(chartView); 
                       window.resize(1000, 1000); 
                       window.show(); /

}
}

[Pl45m4]

@julie546 said in how i can identify and read the columns of a csv file ?:

qreal x = parts.at(0).toFloat(&ok);
if(!ok)
continue;
qreal y = parts.at(1).toFloat(&ok);

Print the values for x and y and check if these are the values from your file.
The code from @KroMignon doesn't look wrong.

[julie546]

@Pl45m4 @KroMignon yes I have checked I have the right values ​​now I have a graph but it is not the same that I do with the csv file, I cannot find the same graph, what do you think please ?

[KroMignon]

@julie546 said in how i can identify and read the columns of a csv file ?:

but it is not the same that I do with the csv file,

What do you mean with not the same?

[julie546]

@KroMignon this is what I found with qt

and this is what I have to find

despite I made qDebug () << x;
qDebug () << y;
and I found the same values with csv file

[julie546]

This post is deleted!

[mrjj]

@julie546
Hi
If you look closely they are the same.
Its just you are using QLineSeries which draws lines between the points so
that why it looks differernt.

Maybe the scatter type can be used
https://doc.qt.io/qt-5/qtcharts-scatterchart-example.html

instead of the LineSeries.

[julie546]

@mrjj
thank you for your reply I have changed it but there are some missing points
QScatterSeries * series = new QScatterSeries;
series->setMarkerShape(QScatterSeries::MarkerShapeRectangle);

[mrjj]

@julie546
Well it does look more like it
so the question if those points go missing during reading or where they go.

What does the draw correct looking diagram ?
I mean what app ?

[julie546]

@mrjj it is a 'lidar tg15' sensor
i did series->append(x, y);
qDebug() << y;
qDebug() << x;
and I found all the points

[mrjj]

@julie546
Ok but the right diagram you showed the picture of.
Did you hand draw this or did an app do it?

since no points is missing im simply wondering if that data would allow the correct diagram at all.

[julie546]

@mrjj
it's from excel

[mrjj]

@julie546
ok. and you used the same CSV file there ?

and you compared the values we insert, value by value to make sure it reads as it should ?

I mean if it could not convert for some reason it would silently continue.

 if(!ok)
   continue;

some of the points to the far right seems more out there than on correct diagram.
should be around 6.0 but is 6.8

[julie546]

@mrjj yes it's from the same csv file
i have on the csv file 1500 value