[ROOT] Scattergram display: statistics change upon axis zoom

From: Tony Colley (tony.colley@itt.com)
Date: Thu Aug 01 2002 - 17:28:38 MEST


Fellow ROOTers:

I have displayed a scattergram. The display is shown in the attached 
before-canvas.gif.

I then use the mouse/cursor to zoom in on a portion of the x axis. The 
statistics within the displayed statistics block automatically generated 
by ROOT change! See the new statistics (for the exact same set of 
points) in the attached after-canvas.gif. The change may not be drastic, 
but it is disconcerting. If one had instead used the mouse/cursor to 
zoom in on a portion of the y axis, the exact same behaviour is noted... 
that is, the statistics change and they change to the same new 
statistics as when zooming on the x axis. When I unzoom, the statistics 
go back to the original statistics.

Now, if I zoom in to where not all of the points are within the zoomed 
range, the statistics change again! Specifically, the number of entries 
remains constant, but the remaining numbers change. If I continue to 
zoom in to reduce the number of points within the displayed range, 
sometimes the statistics change and sometimes they don't.

I noticed this behaviour two or three months ago, and it still occurs 
with my current ROOT. My current configuration is ROOT 3.03/06 (built 10 
July 2002) on a Linux RedHat 7.2 workstation (Dell OptiPlex GX110) using 
gcc 3.0.2.

Another issue: sometimes ROOT refuses to zoom to the range I've drawn 
out with the mouse/cursor. No matter how many times I try, it simply 
refuses to change. It is NOT anywhere near the resolution of float or 
anything... for example, in this scattergram, once I've zoom the y axis 
into the range 40 to 41.6 (which is the y range of the data points), it 
does not want to zoom in any more... no matter how large or narrow a 
band I try to zoom in on. There are many other unexpected behaviours 
with axis zooming, but this is enough for one email.

Cheers,
Tony Colley




before-canvas.gif
after-canvas.gif



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