Qwt/Qt read data from an external file and plot them

[kore]

Hi,
I want to edit the example Scatterplot that comes with Qwt in such a way that i can read data(x and y coordinates) from an external txt file and plot it like the example. I am new in Qt/Qwt/C++, but I learned C# at school.
I know I need QTextStream to read the data but I dont now how to save it in 2 arrays(x and y) and the next problem is I dont now what I need/I can delete from the source code of the example. I'm sorry for my bad english but I need your help D:

mainwindow.cpp:

#include "mainwindow.h"
#include "plot.h"
#include <qmath.h>

static double randomValue()
{
// a number between [ 0.0, 1.0 ]
return ( qrand() % 100000 ) / 100000.0;
}

MainWindow::MainWindow()
{
d_plot = new Plot( this );
d_plot->setTitle( "Scatter Plot" );
setCentralWidget( d_plot );

// a million points
setSamples( 100000 );
}

void MainWindow::setSamples( int numPoints )
{
QPolygonF samples;

for ( int i = 0; i < numPoints; i++ )
{
const double x = randomValue() * 24.0 + 1.0;
const double y = ::log( 10.0 * ( x - 1.0 ) + 1.0 )
* ( randomValue() * 0.5 + 0.9 );

samples += QPointF( x, y );
}

d_plot->setSamples( samples );
}


plot.cpp:

#include "plot.h"
#include <qwt_plot_magnifier.h>
#include <qwt_plot_panner.h>
#include <qwt_plot_picker.h>
#include <qwt_picker_machine.h>
#include <qwt_plot_curve.h>

class DistancePicker: public QwtPlotPicker
{
public:
DistancePicker( QWidget *canvas ):
QwtPlotPicker( canvas )
{
setTrackerMode( QwtPicker::ActiveOnly );
setStateMachine( new QwtPickerDragLineMachine() );
setRubberBand( QwtPlotPicker::PolygonRubberBand );
}

virtual QwtText trackerTextF( const QPointF &pos ) const
{
QwtText text;

const QPolygon points = selection();
if ( !points.isEmpty() )
{
QString num;
num.setNum( QLineF( pos, invTransform( points[0] ) ).length() );

QColor bg( Qt::white );
bg.setAlpha( 200 );

text.setBackgroundBrush( QBrush( bg ) );
text.setText( num );
}
return text;
}
};

Plot::Plot( QWidget *parent ):
QwtPlot( parent ),
d_curve( NULL )
{
canvas()->setStyleSheet(
"border: 2px solid Black;"
"border-radius: 15px;"
"background-color: qlineargradient( x1: 0, y1: 0, x2: 0, y2: 1,"
"stop: 0 LemonChiffon, stop: 1 PaleGoldenrod );"
);

// attach curve
d_curve = new QwtPlotCurve( "Scattered Points" );
d_curve->setPen( QColor( "Purple" ) );

// when using QwtPlotCurve::ImageBuffer simple dots can be
// rendered in parallel on multicore systems.
d_curve->setRenderThreadCount( 0 ); // 0: use QThread::idealThreadCount()

d_curve->attach( this );

setSymbol( NULL );

// panning with the left mouse button
(void )new QwtPlotPanner( canvas() );

// zoom in/out with the wheel
QwtPlotMagnifier *magnifier = new QwtPlotMagnifier( canvas() );
magnifier->setMouseButton( Qt::NoButton );

// distanve measurement with the right mouse button
DistancePicker *picker = new DistancePicker( canvas() );
picker->setMousePattern( QwtPlotPicker::MouseSelect1, Qt::RightButton );
picker->setRubberBandPen( QPen( Qt::blue ) );
}

void Plot::setSymbol( QwtSymbol *symbol )
{
d_curve->setSymbol( symbol );

if ( symbol == NULL )
{
d_curve->setStyle( QwtPlotCurve::Dots );
}
}

void Plot::setSamples( const QVector<QPointF> &samples )
{
d_curve->setPaintAttribute(
QwtPlotCurve::ImageBuffer, samples.size() > 1000 );

d_curve->setSamples( samples );
}

[Uwe]

In your case you have to replace MainWindow::setSamples:

void MainWindow::setSamples( )
{
    QPolygonF samples;
 
    // read your points from file and append them to samples
 
    d_plot->setSamples( samples );
}

void MainWindow::setSamples( )
{
    QPolygonF samples;

    // read your points from file and append them to samples

    d_plot->setSamples( samples );
}

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Uwe

[kore]

Ty Uwe

#include "mainwindow.h"
#include "plot.h"
#include <qmath.h>
#include <qtextstream.h>
#include <QtCore>
#include <QDebug>


MainWindow::MainWindow()
{
d_plot = new Plot( this );
d_plot->setTitle( "Scatter Plot" );
setCentralWidget( d_plot );
bool a=true;
QPolygonF samples;
setSamples( 10 );

QFile file ("C:/koordinaten/koordinaten.txt");
if(file.open(QIODevice::ReadOnly | QIODevice::Text))
{
QTextStream stream(&file);
QString line;
do
{
line=stream.readLine();
if(a)
{
double x=line.toDouble();
a=false;
}else
{
double y=line.toDouble();
a=true;
samples << QPointF( x, y );
}
}while(!line.isNull());

file.close();
d_plot->setSamples( samples );

}
}

I want to read the file koordinaten.txt line 1 = x1, line 2 = y1, line 3 = x2, line 4 = y2....

and i get this issues:
C:\QwtSource\qwt-6.1.3\examples\scatterplot\mainwindow.cpp:-1: In constructor 'MainWindow::MainWindow()':
C:\QwtSource\qwt-6.1.3\examples\scatterplot\mainwindow.cpp:174: warning: unused variable 'x' [-Wunused-variable]
double x=line.toDouble();
^
C:\QwtSource\qwt-6.1.3\examples\scatterplot\mainwindow.cpp:180: error: no matching function for call to 'QPointF::QPointF(<unresolved overloaded function type>, double&)'
samples << QPointF( x, y );
^

can anyone explain it to me where are the issues and what happend.

later I want to edit it in such a way that I can read the dokument like: line1= 2;3 ,line2= 6;9 ...... x1=2,y1=3,x2=6,y2=9

Edit: I found all the issues . Now I only had to edit it in such a way that I can read the dokument like: line1= 2;3 ,line2= 6;9 ...... x1=2,y1=3,x2=6,y2=9

[kore]

Now I had edit the example Scatterplot that comes with Qwt in such a way that i can read data(x and y coordinates) from an external CSV file and plot it like the example.
But now i want to select the properties (x,y,color) over 3 Comboboxes and my problem is that this example (Scatterplot) dont had a folder named Forms or a .ui file.
Now my questions:
Is it possible?
How or where i had to put the QComboBox syntax? because there dont exist an .ui file
Exists a command with which I can create a new window/ui in which appear the combo boxes ?

ty for all answers^^