transform input argument (matrix) of function

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I'm afraid I don't really understand what you're searching for, but
note that your functions can be written without assignment/return:

fun3 <- function(x) invisible(cbind(xy[,1], xy[,2], xy[,1] + xy[,2]))

Cheers,
Michael

On Sat, Nov 17, 2012 at 3:41 PM, Omphalodes Verna
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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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
No, it should not be a three column matrix. When you call a function  
with an appropriate argument and fail fail to assign it to anything,  
the result evaporates.

?'<-'
?assign

Functions generally do not modify objects "in place". If you wanted to  
have df1 be the result of fun2(df1) you would have needed to do this:

df1 <- fun2(df1)

  There are ways to get around that limitation (described in each of  
those help pages), but I think it is better for one to learn ordinary  
functional programming conventions first.
     [,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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as someone either having difficulty in reading the Posting Guide.
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html

David Winsemius, MD
Alameda, CA, USA