Hi, I noticed a perculiarity with TProfile. my_tree->Draw("var1:var2",cuts,"prof"); //option1 gives a slightly different plot to: my_tree->Draw("var1:var2>>myprof,cuts); //option2 Now, the number of points, mean and rms of both plots are the same, so the same data has gone into both. I set the number of bins in myprof to 100 which I believe is the default number of bins when using the "prof" option. Nothing is cut out on the TProfile initialiser, so the number of non zero points are the same for both. The only difference is that a small percentage of the points are in different places. I looked into a very zoomed in region of both plots and it appeared that the bin boundaries are different for option1 and 2. Fits to option2 give better chi squareds than option1, like a 7 or 8% effect, but I haven't looked at enough examples to conclude anything about chi squareds. I would like to understand what exactly is going on. Has anyone else noticed this? Martin
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