How relate and fit histograms using TMinuit or

Hi, it’s me again.

I’m finding some problems to fit a histogram as the sum of other three. I have one data histogram (EXP) and three Monte Carlo histograms (MC1, MC2, MC3), were each MC contributes to the EXP. I would like to know how much each one contributes. In other words, I need something like EXP = w1.MC1 + w2.MC2 + w3.MC3, a simple weighted sum. I’ve tried with TFractionFitter, but I don’t know if it work in this way. I know that it can be done using TMinuit but I don’t know how to relate the four histograms and I didn’t find any example. Does anyone can help me?
I use ROOT 4.00/08, Linux RH9 and gcc 3.4.2.

Dear Sergio,

I believe I’ve answered that in


Dear Frank,

I’m sorry, but I didn’t see you reply at that time. I just saw it this morning.
Thank you. Yes, you answered my question. I have another one. I hope you can help me. Let’s suppose that I have instead of one, two data histograms, and for each one, three MC sources. Is it possible to fit these two data hist. (with their respective MC s) in order to find, at the end, three weights that multiplying the six MC hist. could reproduce the two data hits?

Best wishes,