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Rarity distribution for BDT is non-uniform

Hi,

I’m training a BDT Classifier to reject background events of my data sample to increase the purity. I was reading the TMVA Users Guide and in section 3.1.13 it says:

Another useful aspect of the probability integral transformation (rarity) is the possibility to directly
visualise deviations of a test background (which could be physics data) from the training
sample, by exhibition of non-uniformity

So, I habilitate the “CreateMVAPds” flag and plotted Rarity to check. The result can be seen below.

image

What does it mean? And, how can I avoid it?

I’m passing as signal an MC sample with a cut in the signal region, and for background, I’m passing the wings of mass distribution far from the signal region.

Thanks!

Hi,
It looks then that the distribution from training and test BDT output is very different. You can easily check that by plotting the output distribution train and test ( case 4b in TMVAGui)

Lorenzo

Hi Lorenzo,

Looking TMVAGui 4b option I don’t see a big difference.

image

Hi,
This is very strange. Can you please share the macro and the input data file so I can try to reproduce this problem ?

Cheers

Lorenzo