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

[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

[JonB]

@julie546
As @mrjj said, just to humour us, in the two places you have

        if(!ok)
            continue;

please put in above the if

Q_ASSERT(ok);

(You'll need to have included #include <QtGlobal>, but probably something else you are including will have done this.)

[KroMignon]

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

As @mrjj said, just to humour us, in the two places you have
if(!ok)
continue;

please put in above the if
Q_ASSERT(ok);

The reason why there is continue, is because the CSV file contains the column headers, which are strings and cannot be converted to float.
With Q_ASSERT() the program will be interrupted.

[mrjj]

@KroMignon
ah so it should skip first col. always. good catch.
Im just wondering if all points really get converted as
else i dont see how the graphs can be that differnt.

[JonB]

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

The reason why there is continue, is because the CSV file contains the column header

Surely that's for the first line only?

[julie546]

@JonB @mrjj @KroMignon
I remove the headers and I replace
if (! ok)
continue;
by Q_ASSERT (ok);
but it's the same result

[KroMignon]

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

I remove the headers and I replace
if (! ok)
continue;
by Q_ASSERT (ok);
but it's the same result

I suppose it is a simple precision issue, you should replace toFloat() with toDouble():

while (!filelidar.atEnd()) {
    QString line = filelidar.readLine();
    const auto parts = line.split (',');
    if(parts.size() >= 2)
    {
        bool ok;
        qreal x = parts.at(0).toDouble(&ok);
        if(!ok)
        {
            qDebug() << "Could not parse X value" << parts.at(0);
            continue;
        }
        qreal y = parts.at(1).toDouble(&ok);
        if(!ok)
        {
            qDebug() << "Could not parse Y value" << parts.at(1);
            continue;
        }
        series->append(x, y);
    }
}