Dear list!
 
I would like to write a function to transform matrix, which is input argument of a written function. It is easy with new matrix (see below), but my idea is to transform input argument (matrix) of function without any additional matrixes. Here is an example:

fun1 <- function(xy) {
xy <- cbind(xy[,1], xy[,2], xy[,1] + xy[,2])
return(xy)
}
 
df1 <- matrix(c(1,2,3,1,2,3), ncol = 2)
fun1(df1)
 
fun2 <- function(xy) {
xy <- cbind(xy[,1], xy[,2], xy[,1] + xy[,2])
return(invisible(xy))
}
 
fun2(df1)
df1
> should be
     [,1] [,2] [,3]
[1,]    1    1    2
[2,]    2    2    4
[3,]    3    3    6
 
Thanks to all for help,
OV
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