Hello, i am working with the R.oo package. I want to store objects (instances of classes) in a n-dimensional array. I tried this: t <- array(list(),dim=c(8,8)) t[1,1] <- someObject print(t[1,1]) results in: [[1]] [1] NA the same with any S4 classes setClass("track,representation(x="numeric",y="numeric")) t1 <- new("track",x=1:5,y=5:10) t[1,1] <- t1 Error in "[<-"(`*tmp*`, 1, 1, value = t1) : nothing to replace with Is there any chance not to use a list in list construction? Sincerly Lars Feistner -- ---------------------------------------------------------------------- Lars Feistner feistner at justis.de Untere Neckarstr 32 Tel: +49 6221 8935279 D-69117 Heidelberg Mobil:+49 173 3205195