Dear R- helper, I am trying to analyze repeated measure . there are three factors: a ,b and time a and b factors have two levels and time has 90 different timepoints. This is the r-code I've tried; gls(y~factor(a)*factor(b)*time, data=, corr=corAR1(form=~time|id)) Here, the reason why I did not put factor code in time factor is that the R never gave me results and said "no response". So, I took factor code off. Here is my question. I am not sure my code is correct and I am wondering if time factor can be considered as a random factor so that I can use the R-code below. gls(y~factor(a)*factor(b), data=, corr=corAR1(form=~time|id)) please give me any comments or advice... Thank you for your help. [[alternative HTML version deleted]]