# [R] using matrix data for function

Liaw, Andy andy_liaw at merck.com
Wed Sep 17 20:46:33 CEST 2003

```Don't think this is "best", but here's one way:

> mat <- matrix(1:12, 6)
> mat
[,1] [,2]
[1,]    1    7
[2,]    2    8
[3,]    3    9
[4,]    4   10
[5,]    5   11
[6,]    6   12
> f <- function(x, y) x + y
> apply(mat, 1, function(x) do.call("f", as.list(x)))
  8 10 12 14 16 18

Note that apply(mat, 1, f) won't work, because both values are passed to f
in a single vector.

Perhaps better alternatives are:

1. Re-write f so that it takes a single vector of two elements, or write a
wrapper fw <- function(x) f(x, x), then use fw in apply().

2. Re-write f so that it's vectorized, so that f(mat[,1], fmat[,2]) works.

HTH,
Andy

> -----Original Message-----
> From: Bing Zhang [mailto:bih at ornl.gov]
> Sent: Wednesday, September 17, 2003 2:03 PM
> To: r-help
> Subject: [R] using matrix data for function
>
>
> Hi All,
>
> I have a function, f(x,y)
> I have a matrix of data, m,  with the 1st column is x and the
> 2nd column is y What's the best way to get f(x,y) for each
> row of the matrix? I tried
> result<-f(m[,1],m[,2]) but it doesn't work.
>
> Thanks!
>
> Bing
>
> ---------------------------------
> 1060 Commerce Park
> Oak Ridge National Laboratory
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> Email: zhangb at ornl.gov
>
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>

```