[ROOT] Retrieving Histogram from File

From: Frank Simon (fsimon@cipsuse2.t30.physik.tu-muenchen.de)
Date: Wed Oct 24 2001 - 19:56:40 MEST 

Hi Rooters,

I have a small macro that should read a histogram from file and draw
it in a canvas:


TH2F *hClusterRatio =
(TH2F*) f->Get("ClusterAmpRatioCoord_Smpl02;1");

hClusterRatio->Draw();   //Line 21

I get:

Error: illegal pointer to class object hClusterRatio 0x0 141
FILE:goldenrun.cc LINE:21

When I open the file, and call
ClusterAmpRatioCoord_Smpl02->Draw()

I can display the histogram. However, I also want to make some
modifications, so I need the pointer.

What could be the problem?

I'm using SuSE Linux 7.4 and Root 3.02 precompiled.

Thanks!

Greetings

Frank

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