Hi
I have a function f(k,l) which returns a matrix for integer k and l.
I want to call f(.,.) for each combination of a supplied vector (as
in expand.grid())
and then I want to assemble these matrices into one big one using
k and l to index the position of the submatrices returned by f(k,l).
Toy example follows.
f <- function(k,l){
matrix(k+l , k , l)
}
and I want to call f() with each combination of c(1,3)
for the first argument and c(2,4,5) for the second
and then assemble the resulting matrices.
I can do it piecemeal:
a <- c(1,3)
b <- c(2,4,5)
expand.grid(a,b)
Var1 Var2
1 1 2
2 3 2
3 1 4
4 3 4
5 1 5
6 3 5
cbind(rbind(f(1,2),f(3,2)) , rbind(f(1,4),f(3,4)) , rbind(f(1,5),f
(3,5)))
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11]
[1,] 3 3 5 5 5 5 6 6 6 6 6
[2,] 5 5 7 7 7 7 8 8 8 8 8
[3,] 5 5 7 7 7 7 8 8 8 8 8
[4,] 5 5 7 7 7 7 8 8 8 8 8
[see how the calls to f(. , .) follow the rows of expand.grid(a,b)]
How to do this in a nice vectorized manner?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
a crude approach is the following:
f <- function(x){
k <- x[1]
l <- x[2]
matrix(k + l, k , l)
}
a <- c(1, 3)
b <- c(2, 4, 5)
combs <- expand.grid(a, b)
do.call("cbind", lapply(split(combs, combs$Var2), function(x)
do.call("rbind", apply(x, 1, f))))
I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Robin Hankin" <r.hankin at noc.soton.ac.uk>
To: "RHelp" <r-help at stat.math.ethz.ch>
Sent: Wednesday, November 16, 2005 11:10 AM
Subject: [R] matrix assembly
> Hi
>
> I have a function f(k,l) which returns a matrix for integer k and l.
> I want to call f(.,.) for each combination of a supplied vector (as
> in expand.grid())
> and then I want to assemble these matrices into one big one using
> k and l to index the position of the submatrices returned by f(k,l).
>
> Toy example follows.
>
>
> f <- function(k,l){
> matrix(k+l , k , l)
> }
>
> and I want to call f() with each combination of c(1,3)
> for the first argument and c(2,4,5) for the second
> and then assemble the resulting matrices.
>
> I can do it piecemeal:
>
> a <- c(1,3)
> b <- c(2,4,5)
> expand.grid(a,b)
> Var1 Var2
> 1 1 2
> 2 3 2
> 3 1 4
> 4 3 4
> 5 1 5
> 6 3 5
> cbind(rbind(f(1,2),f(3,2)) , rbind(f(1,4),f(3,4)) , rbind(f(1,5),f
> (3,5)))
> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11]
> [1,] 3 3 5 5 5 5 6 6 6 6 6
> [2,] 5 5 7 7 7 7 8 8 8 8 8
> [3,] 5 5 7 7 7 7 8 8 8 8 8
> [4,] 5 5 7 7 7 7 8 8 8 8 8
>
> [see how the calls to f(. , .) follow the rows of expand.grid(a,b)]
>
>
> How to do this in a nice vectorized manner?
>
>
>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
On 11/16/05, Robin Hankin <r.hankin at noc.soton.ac.uk> wrote:> Hi > > I have a function f(k,l) which returns a matrix for integer k and l. > I want to call f(.,.) for each combination of a supplied vector (as > in expand.grid()) > and then I want to assemble these matrices into one big one using > k and l to index the position of the submatrices returned by f(k,l). > > Toy example follows. > > > f <- function(k,l){ > matrix(k+l , k , l) > } > > and I want to call f() with each combination of c(1,3) > for the first argument and c(2,4,5) for the second > and then assemble the resulting matrices. > > I can do it piecemeal: > > a <- c(1,3) > b <- c(2,4,5) > expand.grid(a,b) > Var1 Var2 > 1 1 2 > 2 3 2 > 3 1 4 > 4 3 4 > 5 1 5 > 6 3 5 > cbind(rbind(f(1,2),f(3,2)) , rbind(f(1,4),f(3,4)) , rbind(f(1,5),f > (3,5))) > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] > [1,] 3 3 5 5 5 5 6 6 6 6 6 > [2,] 5 5 7 7 7 7 8 8 8 8 8 > [3,] 5 5 7 7 7 7 8 8 8 8 8 > [4,] 5 5 7 7 7 7 8 8 8 8 8 > > [see how the calls to f(. , .) follow the rows of expand.grid(a,b)] > > > How to do this in a nice vectorized manner? >Replacing your example with the appropriate do.call and lapply calls gives this: do.call("cbind", lapply(b, function(x) do.call("rbind", lapply(a, f, l = x)))) or one can do the cbind in the inner loop and the rbind in the outer giving the same result: do.call("rbind", lapply(a, function(x) do.call("cbind", lapply(b, f, k = x))))