Hi Jason, There is no such function in ROOT returning the fit error for a given value of x. You have to use the cov matrix and compute the function value with ffgr->Eval(x). If you implement this function, send it to me. I will include it in the source. Rene Brun On Sun, 20 Jul 2003, Jason Seely wrote: > hi ROOT people, > > i am just wondering if there is an easy way to get the error of a fit. > i'm fitting something like this (for example) > > ffgr = new TGraphErrors(imax, x, y, dx, dy); > ffgr->Fit(func,"","",xmin,xmax); > > TF1 *fitfunc; > fitfunc = ffgr->GetFunction(func); > > so once i have the fitting function, i know how to get parameters, > chi^2, parameter errors, etc. what i want is the estimated error on the > function itself so i can draw an error band. i've seen a lot of stuff > in ROOTtalk about how to get the covariance matrix, so i can do that to > calculate the error myself from the covariance matrix, but it seems like > there must be something like > > ffgr->GetError(x), or ffgr->EvalError(x), or whatever > > to get the error as calculated from the covariance matrix so i don't > have to do all the work myself. any ideas? > > thanks, > > jason >
This archive was generated by hypermail 2b29 : Thu Jan 01 2004 - 17:50:13 MET