TH2 fill with binned data then change axis limits

[Martha_Hilton]

Hi I wonder if someone can help me.
I am trying to do the following:

• Fill a TH2 with binned data (pre-defined axis limits and bins) with SetBinContent()
• Draw the histogram on a new axis with extended axis range.
  So I try this:

kernel_hist = TH2F("kernel", "Kernel PDF", 100, phsp.lowerLimit(1), phsp.upperLimit(1),
                                           100, phsp.lowerLimit(2), phsp.upperLimit(2))
for i in range(100):
    for j in range(100):
        kernel_hist.SetBinContent(i, j, hist2d[i,j])

then:

kernel_hist.Draw("zcol")
kernel_hist.GetXaxis().SetTitle("M^{2}(K_{S}#pi), GeV")
kernel_hist.GetYaxis().SetTitle("M^{2}(#pi#pi), GeV")
kernel_hist.GetXaxis().SetLimits(0,3.5)
kernel_hist.GetYaxis().SetLimits(0,2.0)

What happens is the histogram is stretched along with the axes.
Is there a way of changing the axes without changing the histogram?

ROOT Version: 6.18/04

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[Wile_E_Coyote]

Well, “SetLimits” changes the full range which was set at histogram’s creation time.
Maybe you actually want:

kernel_hist.GetXaxis().SetRangeUser(0., 3.5)
kernel_hist.GetYaxis().SetRangeUser(0., 2.0)

[Martha_Hilton]

Hi so when I try SetRangeUser it seems to have no effect and the axes have the original limits. This has been mentioned in previous questions on the forum but I can’t find a solution. Any other ideas?

Many thanks for your response.

[Wile_E_Coyote]

Maybe you should first modify the axes (“SetLimits” or “SetRangeUser”) and only then call “Draw”.

[Martha_Hilton]

I’m afraid this did not work either.
The solution I found was to redefine the bins to leave some empty bins on either side of my histogram. This is a bit of a work-around though since the binning was predefined so had to add bins of a certain size and leave the content as zero in order to get a wider axis range.

[couet]

May be you can also draw first the “frame” with the limits you needs using gPad->DrawFrame() and then draw your histogram using option SAME.