Hello Friends,

I am not new by Qt, however I am using the first time the Qwt library for my Purposes. Well, My Questions are following:
a-) How can I get the x-axis of my Histogram scaled with strings instead with numbers ?
b-) what does mean "intervals" and "values" in the following code. I understood it as "intervals" means the distance between each two beam (y-axis) and "value" means the value of this beam (x-axis) !

QwtArray<QwtDoubleInterval> intervals(numValues);
QwtArray<double> values(numValues);

double pos = 0.0;
for ( int t = 0; t < (int)intervals.size(); t++ )
{
const int width = 5 + rand() % 5; //15;
const int value = rand() % 100;

intervals[t] = QwtDoubleInterval(pos, pos + double(width));
values[t] = 120; //value;

pos += width;
}

c-) I just have to make a histogram for exactly 7 parameters (x-axis) looking like this:

the x-axis MUST like this:

|------------|------------|-------------|------------|------------|-----------|
ABB BCC CDD DEE EFF GFF PPP

Question: How can I can determine the width of each beam that I have use in order to calculate the "interval" ? I have tried all Qwt-Examples, but I do not understand the Calculation's philosophy behind that, so I can not move on. Please I need your help.
Thanks.