[R] inserting rows into a matrix
Gabor Grothendieck
ggrothendieck at gmail.com
Thu Jul 27 16:36:45 CEST 2006
Try this where f and A2 are as in your post:
out <-f(A2[A2>0])
replace(matrix(0, length(A2), ncol(out)), A2 > 0, out)
On 7/27/06, Robin Hankin <r.hankin at noc.soton.ac.uk> wrote:
> Hi
>
>
> I have a little vector function that takes a vector A of strictly
> positive integers
> and outputs a matrix M each of whose columns is the vector, modified in
> a complicated combinatorical way.
>
> Now I want to generalize the function so that A can include zeroes.
> Given A,
> I want to strip out the zeroes, pass it to my function, and pad M
> with rows at positions corresponding to the zeroes of A.
>
> Commented, minimal, self-contained, reproducible toy example follows.
>
>
> f <- function(a){cbind(a,a+1,rev(a))} #real function a ghastly
> nightmare
>
> A <- 1:5
> f(A)
> a
> [1,] 1 2 5
> [2,] 2 3 4
> [3,] 3 4 3
> [4,] 4 5 2
> [5,] 5 6 1
>
>
> # f() works as desired.
>
> # Now introduce A2, that includes zeroes. In my application, f(A2)
> would fail
> because of the zeroes.
>
> A2 <- c(1,0,0,2,4,0,3)
>
> I can strip the zeroes out and call f():
> f(A2[A2>0])
> a
> [1,] 1 2 3
> [2,] 2 3 4
> [3,] 4 5 2
> [4,] 3 4 1
>
> which is fine. How to put the zeroes back in in the appropriate rows
> and get the following:
>
> > cbind(c(1,0,0,2,4,0,3),c(2,0,0,3,5,0,4),c(3,0,0,4,2,0,1))
> [,1] [,2] [,3]
> [1,] 1 2 3
> [2,] 0 0 0
> [3,] 0 0 0
> [4,] 2 3 4
> [5,] 4 5 2
> [6,] 0 0 0
> [7,] 3 4 1
> >
>
>
>
> anyone?
>
>
>
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
> tel 023-8059-7743
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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