I was getting some strange results adding two matrices together, when I eventually worked out that one of them was a data frame (they both look the same when you print them!). I was surprised to discover the following behaviour: 1) When a matrix is added to a data frame, they do not have to conform. In fact the matrix is treated like a vector. 2) When a vector is added to a data frame, there is no check to see if the number of rows in the data frame is a multiple of the vector length. Even more surprisingly, this is exactly the same as the behaviour of S-PLUS. Bug or feature? Martyn -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._