On 24/09/14 03:10, carol white wrote: > Hi, If I want to divide the column of a matrix by the sum of the > column, should I loop over the columns or can I use apply family? m1 <- apply(m,2,function(x){x/sum(x)}) should do what you want IIUYC. cheers, Rolf Turner -- Rolf Turner Technical Editor ANZJS