How do I change plot scale based on the selection

I'm plotting 5000 values of histogram(used from TV Plot example), on QwtPlot which has a scroll area. So the xBottom tick values are shown according to my step size in setAxisScale.
The graph is shown with certain number of samples between two major ticks. Assume like this is monthly data.
Now I want to provide an option where user selects the weekly data, then the graph should be plotted for weekly data. The monthly data graph should look crowded one, but the weekly data plot should look a bit relaxed compared to monthly. But when the user selects the daily data option, the scale should be even relaxed.

What I mean is the distance between two ticks should always be same. But the tick values, number of values between two ticks and graph width should differ based on each selection. How do I implement this?

I'm guessing you just need to set x axis range (upper and lower values, like zooming).
That will stretch therange set (month/week) to fit in the visible area.
The distances between ticks will still be the same but less data (in more 'relaxes' fashion) will be visible.