Dear Alexandre, > for(typeD in 1:Dist){ > k <- fitdistr(BD,typeD[Dist]) Your code should probably read "for(typeD in 1:length(Dist))" or "for(typeD in seq_along(Dist)". Then, instead of "typeD[Dist]", make it "Dist[typeD]". Please see if that helps. Best, microbiomics