display a plot point by point

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 :)

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 :)

Can we see the code?

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

Code:

---

#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();
}

---

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

So where is your timer code?

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 .

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.

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 !

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).

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

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:

Code:

---

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);
}

---

hello ,
thanks for the skeleton,i'm trying to apply your idea but i get blocked is something .
when i define the macro Q_OBJECT an error appear :

Code:

---

undefined refrence to vtabe for plot

---

my .pro is :

Code:

---

TEMPLATE = app
TARGET =
DEPENDPATH += .
INCLUDEPATH += C:\svn\qwt\qwt\src
LIBS += C:\svn\qwt\qwt\lib\qwtd5.dll
CONFIG += debug
 
# Input
SOURCES += main.cpp

---

main.cpp :

Code:

---

class Plot : public QwtPlot
{
//Q_OBJECT
    public:
        Plot();
      void pointByPoint();
 
    private :
       QwtPlotCurve *curve1;
       int currentPointPosition;
        QTimer *timer;
        double *x;
        double *y;
 
/*
    public slots:
        void onTimeout(); */
};
 
 
Plot::Plot()
{
    x=new double[100];
    y=new double[100];
 
    for(int i=0;i<100;i++){
        x[i]=i;
        y[i]=i*i;
    }
 
  //......
 
    timer = new QTimer();
  //connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
 
}
 
/*
void Plot::onTimeout(){             //each timeout data will
  currentPointPosition++;           // be added to the curve
  if(currentPointPosition>100) currentPointPosition = 1;
  curve1->setData(x, y1, currentPointPosition);
}
*/
 
void Plot::pointByPoint(){ //calling this method provoque painting curve "slowly"
    while(true){
        timer->start(500);
    }
}
 
 
int main(int argc, char **argv)
{
    QApplication a(argc, argv);
 
    Plot *myPlot = new Plot();
    myPlot->autoRefresh();
    myPlot->resize(600,400);
    myPlot->show();
 
    //myPlot->pointByPoint();
 
    return a.exec();
}

---

thanks for your help :)

Did you remember to run qmake after you added the macro?

ohhh ,sorry ,i'm working with Qt creator and i forgot about qmake !!
thanks a lot :)
it works first time but now :
this code still make error : undefined reference to "vtable for plot"

Code:

---

class Plot : public QwtPlot
{
Q_OBJECT
    public:
      Plot();
      void pointByPoint();
 
    private :
       QwtPlotCurve *curve;
       int currentPointPosition;
       QTimer *timer;
       double *x;
       double *y;
 
    public slots:
        void onTimeout();
};
 
 
Plot::Plot()
{
    x=new double[100];
    y=new double[100];
 
    for(int i=0;i<100;i++){
        x[i]=i;
        y[i]=i*i;
    }
 
    //........
 
   timer = new QTimer();
   connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
}
 
 
void Plot::onTimeout(){             //each timeout data will
  currentPointPosition++;           // be added to the curve
  if(currentPointPosition>100) currentPointPosition = 1;
  curve->setData(x, y, currentPointPosition);
}
 
 
void Plot::pointByPoint(){ //calling this method provoque painting curve "slowly"
    for(int i=0;i<200;i++){
        timer->start(500);
    }
}
 
 
int main(int argc, char **argv)
{
    QApplication a(argc, argv);
 
    Plot *myPlot = new Plot();
    myPlot->autoRefresh();
    myPlot->resize(600,400);
    myPlot->show();
 
    myPlot->pointByPoint();
 
    return a.exec();
}

---

it's a shame to ask many questions but there is no documentation about qwt and i'm still beginner .
thanks for your help :)

Your issues are not related to Qwt. I'm even thinking about moving the thread to the newbie section of the board.

The Q_OBJECT macro has to be placed in a header file (with .h extension). It's possible to place it in an implementation file but it requires some additional work so let's try avoiding it for now. So if your class declaration is in an implementation (.cpp) file, move it to a header file, add the file to your project and rerun qmake and make.

ok, i did but macro problem persist like this :

D:/P2M/courbe/debug/courbe.exe exited with code 0
Starting D:/P2M/courbe/debug/courbe.exe...
D:/P2M/courbe/debug/courbe.exe exited with code -1073741819

if i make macro and slots as a comment everything seems work !

thx again :)

If your application crashes, it's not because of lack or presence of Q_OBJECT macro. Use a debugger to see where it crashes and why.

i don't know how to debug in console mode but i tried with qt creator .
when i run debug mode ,it still running with no information given ,debugger don't run until the first break point , it's written dbg running .

plot.h :

Code:

---

#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
{
Q_OBJECT
    public:
      Plot();
      ~Plot();
      void pointByPoint();
 
    private :
       QwtPlotCurve *curve;
       int currentPointPosition;
       QTimer *timer;
       double *x;
       double *y;
 
    public slots:
        void onTimeout();
};

---

plot.cpp :

Code:

---

#include "plot.h"
 
Plot::Plot()
{
    x=new double[100];
    y=new double[100];
 
    for(int i=0;i<100;i++){
        x[i]=i;
        y[i]=i*i;
    }
 
   currentPointPosition=1;
 
   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
   curve = new QwtPlotCurve("Vitesse");
   curve->setPen(QPen(Qt::green));
   curve->attach(this);
   curve->setData(x, y, currentPointPosition);
 
     //  ...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);
 
   timer = new QTimer();
   connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
}
 
 
void Plot::onTimeout(){             //each timeout data will
  currentPointPosition++;           // be added to the curve
  if(currentPointPosition>100) currentPointPosition = 1;
  curve->setData(x, y, currentPointPosition);
}
 
 
void Plot::pointByPoint(){ //calling this method provoque painting curve "slowly"
    for(int i=0;i<200;i++){
        timer->start(500);
    }
}
 
Plot::~Plot(){
    delete x;
    delete y;
}

---

main.cpp

Code:

---

#include "plot.h"
 
int main(int argc, char **argv)
{
    QApplication a(argc, argv);
 
    Plot *myPlot = new Plot();
    myPlot->autoRefresh();
    myPlot->resize(600,400);
    myPlot->show();
 
    myPlot->pointByPoint();
 
    return a.exec();
}

---

.pro :

Code:

---

TEMPLATE = app
TARGET = 
DEPENDPATH += .
INCLUDEPATH += C:\svn\qwt\qwt\src
LIBS += C:\svn\qwt\qwt\lib\qwtd5.dll
CONFIG += debug
 
# Input
SOURCES += main.cpp \
    plot.cpp
HEADERS += plot.h

---

i made as comment Q_OBJECT and my slot and it works ,i checked debugger too,it's ok with it under Qtcreator .

I'm sorry but I won't debug your code for you, you have to do that.

No , I'm sorry ,
i show the code cuz i suppose there is a simple mistake i can't see it as a Qt beginner .