Hi, I’ve a couple of data file (x,y) I wrote a macro…but I get error [Error] In attachment data file (datafit.txt) and the macro (grafico.c) datifit.txt (358 Bytes) grafico.c (2.0 KB) _ROOT Version:5.34/36 _Platform:Windows 10 _Compiler:Devc++

Good morning…maybe I solved I forgot to transform one value in cm to m…then it changed the fit function I had to use y^2 values, not y value Transforming um to m, i did by excel this operation 2 times Now it works! I got the fit! Thank you for your help!