display a plot point by point

[oswalidos]

hello
i finally downloaded qwt from svn and everything is ok (Qt 4.5 ,qwt 5.3.0,windows xp)
now i need to display a plot point by point ,so i tried to create a retard with Qtimer ,but it doesn't work !

no execution or complilation errors but i haven't the result i'm expecting
it's my first program with qwt ,i'm following the pdf given with qwt 5.1.1
the documentation for qwt 5.1.1 still useful ?

thanks in advance

[oswalidos]

maybe i'm not clear
i simply want to see plot painting point by point because i'm working on a "real-time" application ,points will be available while my system is running ,so i plan to use Qthread to synchronize tasks .
now i need to know how can i control displaying plots ?
can i find signals or create signals to do such thing ?
thanks for your help

[wysota]

Can we see the code?

[oswalidos]

i just tried a code which stored data first ,after it display the curve

#include <QtGui>
#include <qwt_plot.h>
#include <qwt_plot_curve.h>
#include <qwt_plot_marker.h>
#include <qwt_plot_curve.h>
#include <qwt_legend.h>
#include <qwt_series_data.h>
#include <qwt_text.h>
#include <math.h>
 
class Plot : public QwtPlot
{
public:
    Plot();
};
 
Plot::Plot()
{
    double x[100];
    double y1[100];
    double y2[100];
 
    for(int i=0;i<100;i++){
        x[i]=i;
        y1[i]=i*i;
        y2[i]=i;
    }
 
 
    setTitle("Vitesse et angle de braquage en fonction du temps");
    insertLegend(new QwtLegend(), QwtPlot::RightLegend);
 
    // Set axes
    setAxisTitle(xBottom, "Temps");
    setAxisScale(xBottom, 0.0, 100);
 
    setAxisTitle(yLeft, "");
    setAxisScale(yLeft, 0.0, 100);
 
     // add curves
    QwtPlotCurve *curve1 = new QwtPlotCurve("Vitesse");
    curve1->setPen(QPen(Qt::green));
    curve1->attach(this);
    curve1->setData(x, y1, 100);
 
    QwtPlotCurve *curve2 = new QwtPlotCurve("Angle de Braquage");
    curve2->setPen(QPen(Qt::red));
    curve2->attach(this);
    curve2->setData(x, y2, 100);
 
    //  ...a horizontal line ...
    QwtPlotMarker *mY = new QwtPlotMarker();
    mY->setLabel(QString::fromLatin1("t ( ms )"));
    mY->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mY->setLineStyle(QwtPlotMarker::HLine);
    mY->attach(this);
 
    //  ...a vertical line ...
    QwtPlotMarker *mX = new QwtPlotMarker();
    mX->setLabel(QString::fromLatin1("V ( m/s ) ,Ang ( rad/s )"));
    mX->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mX->setLineStyle(QwtPlotMarker::VLine);
    mX->attach(this);
 
}
 
 
int main(int argc, char **argv)
{
    QApplication a(argc, argv);
 
    Plot *myPlot = new Plot();
    myPlot->autoRefresh();
 
    myPlot->resize(600,400);
    myPlot->show();
 
    return a.exec();
}

#include <QtGui>
#include <qwt_plot.h>
#include <qwt_plot_curve.h>
#include <qwt_plot_marker.h>
#include <qwt_plot_curve.h>
#include <qwt_legend.h>
#include <qwt_series_data.h>
#include <qwt_text.h>
#include <math.h>

class Plot : public QwtPlot
{
public:
    Plot();
};

Plot::Plot()
{
    double x[100];
    double y1[100];
    double y2[100];

    for(int i=0;i<100;i++){
        x[i]=i;
        y1[i]=i*i;
        y2[i]=i;
    }


    setTitle("Vitesse et angle de braquage en fonction du temps");
    insertLegend(new QwtLegend(), QwtPlot::RightLegend);

    // Set axes
    setAxisTitle(xBottom, "Temps");
    setAxisScale(xBottom, 0.0, 100);

    setAxisTitle(yLeft, "");
    setAxisScale(yLeft, 0.0, 100);

     // add curves
    QwtPlotCurve *curve1 = new QwtPlotCurve("Vitesse");
    curve1->setPen(QPen(Qt::green));
    curve1->attach(this);
    curve1->setData(x, y1, 100);

    QwtPlotCurve *curve2 = new QwtPlotCurve("Angle de Braquage");
    curve2->setPen(QPen(Qt::red));
    curve2->attach(this);
    curve2->setData(x, y2, 100);

    //  ...a horizontal line ...
    QwtPlotMarker *mY = new QwtPlotMarker();
    mY->setLabel(QString::fromLatin1("t ( ms )"));
    mY->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mY->setLineStyle(QwtPlotMarker::HLine);
    mY->attach(this);

    //  ...a vertical line ...
    QwtPlotMarker *mX = new QwtPlotMarker();
    mX->setLabel(QString::fromLatin1("V ( m/s ) ,Ang ( rad/s )"));
    mX->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mX->setLineStyle(QwtPlotMarker::VLine);
    mX->attach(this);

}


int main(int argc, char **argv)
{
    QApplication a(argc, argv);

    Plot *myPlot = new Plot();
    myPlot->autoRefresh();

    myPlot->resize(600,400);
    myPlot->show();

    return a.exec();
}

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i want to change this code to display the curve step by step from (0,0) until (n,m) while time progressing !

[wysota]

So where is your timer code?

[oswalidos]

i don't know where should i put timer .
i'm asking how can i put timer ?
i may should use other classes not Qwtplot cuz it needs the data stored to display curves .
i tried with timer somewhere but it doesn't seem to work !
i think i have to use others classes or some signals to control painting process .

[wysota]

You should start a timer somewhere in your code and connect its timeout() signal to a custom slot that you have to implement. Inside the slot simply add more data to the curves.

[oswalidos]

all data is fixed in constructor and can't be anywhere else .
i think constructor can't be dynamic ,it's fixed since we instance an object from its class .
if constructor still running when application is running that's mean is using more than thread ,that's can be right ?
can i call constructor many times to change object's value and display it using timer ? i don't think so !

[wysota]

In the constructor you can store the data in some array. Then you can add the data to the plot in some other place (like a slot).

[oswalidos]

thanks for your help ,
i'll try but logically data in constructor should be given only one time .

[wysota]

I think you don't understand me. You can keep the data in two places - one of them is initialized and filled with data in the constructor. The other is the plot itself that is fed with the data from the first container using a timer.

Here is a skeleton of a code doing what I mean:

X::X(){
  for(int i=0;i<100;i++){
    x[i]=i;
    y1[i]=i*i;
    y2[i]=i;
  }
  curve1 = new QwtPlotCurve("Vitesse"); // curve1 is a member variable
  currentPointPosition = 1; // currentPointPosition is a member variable
  updateData();
  QTimer *timer = new QTimer(...);
  connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout())); 
  timer->start(500);
//...
}
 
void X::onTimeout(){
  currentPointPosition++;
  if(currentPointPosition>100) currentPointPosition = 1;
  updateData();
}
 
void X::updateData(){
  curve1->setData(x, y1, currentPointPosition);
}

X::X(){
  for(int i=0;i<100;i++){
    x[i]=i;
    y1[i]=i*i;
    y2[i]=i;
  }
  curve1 = new QwtPlotCurve("Vitesse"); // curve1 is a member variable
  currentPointPosition = 1; // currentPointPosition is a member variable
  updateData();
  QTimer *timer = new QTimer(...);
  connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout())); 
  timer->start(500);
//...
}

void X::onTimeout(){
  currentPointPosition++;
  if(currentPointPosition>100) currentPointPosition = 1;
  updateData();
}

void X::updateData(){
  curve1->setData(x, y1, currentPointPosition);
}

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