Sumw2() for empty bin?

From: William Love <>
Date: Wed, 13 Jul 2005 11:03:12 -0400

Root help:

  I have a large number of (2D) histograms with simple event counts in the bins. When  I do Sumw2() to set the errors it appears the empty bins have their error set to zero.  This plays havoc with the Chi squared calculation (crash on divide by zero). Is there a  way to make Sumw2() set the error on empty bins to 1.0?

                          Bill Love 

      Using root  4.04.02  on RedHat Linux.                                        
Received on Wed Jul 13 2005 - 16:55:36 MEST

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