I was wondering why this loop doesn't work! for (i in 1:k) fnTr[i] <- function (p) 0.5* sum ( n*log(2*pi) - log(sd(i)^2) +(logitp(i)-p)^2/sd(i)^2 ) outTr[i]<- nlm (fnTr[i],p=c(10),hessian=TRUE) minimumTr[i] <- outTr[i]$minimum valueTr[i] <- outTr[i]$estimate list (minimumTr[i],valueTr[i]) Has anyone can help me? Thank you very much Hathaikan