Shared parameter in TF1 function

Roofit and RooStats
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Is there an easy way to share a parameter in a TF1 function?
Something like func1->ShareParameter(…) ?

I have two data sets which follow a a/x^b function, whereby the parameter b (the slope) is the same for both data sets.

Thanks :blush:

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Hi Mary, Queen of Scots, welcome to the forum :slight_smile:

…and the other parameters are expected to be different for the two samples, right? @moneta will probably give you a better answer - my “preliminary” one is:

You could have two nested minimizations:

  1. outer: find the optimal b
  2. inner: find optimal parameters for set 1 (given b), find optimal parameters for set 2 (given the same b), return the sum of \chi^2 (or whatever it is you’re using as the goodness of fit measure) from set 1 and 2 as the goodness of fit for b.
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Hi,

I guess what you would like to do is a combined fit to the two data set. For doing this, look at this tutorial:

Cheers

Lorenzo

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Yessssss! That is exactly what I was looking for! Thanks a lot :slight_smile:

I already integrated this in my code and it works.

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