search for: agrm

...describes how to format the correlation matrix to pass to functions lme and gls. Basically, the correlation matrix has to be one of the corStruct classes, probably corSymm for your example. So in the call to lme (or gls if you really have no random effects), use something like: correlation=corSymm(AGRM[lower.tri(AGRM)], fixed=TRUE). Anyway, it's all there in the book. HTH, Simon. Simon Blomberg, PhD Depression & Anxiety Consumer Research Unit Centre for Mental Health Research Australian National University http://www.anu.edu.au/cmhr/ Simon.Blomberg at anu.edu.au +61 (2) 6125 3379 &g...