in qwt plot selected region need to find max graph line point

[chandrasekhar.embedded]

Hi ,all i generated plot between x-coordinates and intensities,now my problem is i need to identify on the curve selected region need to find the max graph line point ,for better understand like http://postimg.org/image/an4lh1h8p/ ,suggestions please

[Uwe]

Well the peaks can be found from analysing your samples only. What extra information do you need from its visual representation ( = the plot ) ?

Uwe

[chandrasekhar.embedded]

when ever we select one region on graph http://postimg.org/image/an4lh1h8p/ that time only with in the region points only need to find max point (this part i have idea) ,my problem is how will start curve data comparing from rubberband start region to rubberband end region .please suggest similar examples or posts,thank you.

[HappyCoder]

Just an idea:
Your curve data and your rubberband can both transformed into a QPolygonF.
QPolygon::intersected returns a QPolgonF with intersected data of curve.
Iterate of that to find max value.

[chandrasekhar.embedded]

thankyou ,now with this am able to select region and find max point in the selected region but some times getiing exception http://postimg.org/image/5divnym4l/ ,left side selected many regions worked fine but right side selected region giving exception ASSERT failure in QVector<T>:perator[]: "index out of range", file ..\..\..\Qt\Qt5.5.0\5.5\mingw492_32\include/QtCore/qvector.h, line 397
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.
How to solve this exception ,suggestions please.
connect(rectPicker, SIGNAL(selected( QRectF)),this,SLOT( click_on_graph(QRectF)));


void Mainwindow::click_on_graph( QRectF a)
{
qDebug()<<"list\n"<<a;
long int start,end,i;double maxvalue=0;
start=a.left();
end=a.right();
qDebug()<<"a.left="<<start<<"a.right="<<end;
for(int i = start; i < end; i++) {
double intensity = curve->sample(i).y();
qDebug()<<"curve samples="<<curve->sample(i).y();
if (intensity > maxvalue)
maxvalue = intensity;
}
qDebug()<<"maxintensity="<<maxvalue;

}