RE: TH1 Documentation confusion Projection X,Y

From: Donald McCallum <>
Date: Fri, 24 Jun 2005 11:46:39 -0400


   I am uncertain about the correct bins to use when doing a projection from a 2-D histogram. The documentation for ProjectionX states that it is a projection from channels along the Y axis onto the X-axis and to use the bins along the Y-axis, i.e. first_ybin, last_ybin. However, for a ProjectionY, for which it is stated that this is a projection from channels along the X-axis onto the Y-axis, it also states that the bins to use are first_ybin and last_ybin. Should this perhaps be first_xbin, last_xbin instead?

  This is a little confusing, and it appears in all documentation regarding projections, i.e. in TH1, TH2, etc. Could you please tell me definitively which axis binning is to be used with which projection, i.e y_bins with ProjectionX and x_bins with ProjectionY, or y_bins with ProjectionY and x_bins with ProjectionX? Received on Fri Jun 24 2005 - 17:50:12 MEST

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