# <ROOT::Math::Fitter::SetFCN>: FCN function has zero parameters

Hi experts,
when I use roofit to calculate the profile likelihood, I encounter errors as following picture. The parameters of interest in this process is “kappa” and “kappa_t”. The RooHistPdf is 2 dimension.
By the way, what’s is the FCN function?

Hi,

The FCN is the function you are minimising (e…g. .the negative log-likelihood). It seems you are performing a minimisation of a function of zero parameter(i.e. a constant) . Probably you are fixing the two parameter of interest kappa and kappa_t but you don’t have any other free parameters in your likelihood .You don’t need to profile then, but just evaluate the likelihood at the two given values of kappa and kappa_t. .

Lorenzo

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