How can I calculate the centroid of counts in a region?
unix% dmstat "acisf01838N002_evt2.fits[sky=circle(4072,4252,36)][bin sky=1]" centroid=yes EVENTS_IMAGE(x, y) min: 0 @: ( 4063 4218 ) max: 85 @: ( 4073 4246 ) cntrd[log] : ( 35.978616181 34.095750477 ) cntrd[phys]: ( 4070.9786162 4249.0957505 ) good: 4053 null: 1276
From top to bottom, the output reports the value and location (in physical coordinates) of the minimum and maximum pixel values, the location of the centroid of the pixel distribution in both logical and physical coordinate systems, the number of valid ("good") pixels, and the number of invalid (i.e. the value equals the Null/NaN value) pixels.
The help file has further details on how these values are calculated.