Error associated to TF1 minimum

ROOT
1

Hello, I have a TF1 with some parameters that I use to fit a TGraphErrors. I want to know the minimum of that function with its error. I obviusly can use GetMinimum for the value, but how can i calculate the error?
Thanks

2

I think @moneta can help.

3

Hi,

If you have an analytical formula for your function minimum that you can differentiate, you can use standard error propagation from the fit covariance matrix. Otherwise, you need to use some MC simulation. You generate a set of different data (TGraphErrors) similar to the one you have and you fit each one of them and then you look at the distribution of the minimum values that you obtain. You can assign then an error from the standard deviation of that distribution.

Best regards

Lorenzo

4

Try to rewrite the fit function so that the “minimum” becomes one of its parameters. Then the fit procedure will automatically give you its error, too.

5

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