Re: [R] Help with matrix manipulation

From: Simon Blomberg <blomsp_at_ozemail.com.au>
Date: Fri 28 Jul 2006 - 17:14:37 EST

apply is your friend:

fn <- function (x, a, b) {
    if (x < a) return(a) else
    if (x > b) return(b) else

    x
    }

apply(mat, c(1,2), fn, -4, 3)

     [,1] [,2] [,3] [,4]

[1,]   -4   -1    3   -4
[2,]   -4    0    3   -3
[3,]   -3    1    3   -2
[4,]   -2    2   -4   -1

HTH, Simon.

Kartik Pappu wrote:
> Hi all,
>
> I have a square (a x a) matrix with values in a range. For example:
>
> [,1] [,2] [,3] [,4]
> [1,] -5 -1 3 -4
> [2,] -4 0 4 -3
> [3,] -3 1 5 -2
> [4,] -2 2 -5 -1
>
> I want to take any number smaller than -4 (in this example -5) and
> replace it with -4 and similarly take any number greater than 3 (in
> this case 4 and 5) and replace it with 3. The other numbers (and the
> overall structure of the matrix should remain unchanged.
>
> Seems like something that would use an "if a<b then c else d" kind of
> logic, but I cannot figure out how to manipulate the entire matrix.
>
> Thanks much
>
> Kartik
>
> ______________________________________________
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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.
>
>

-- 
Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
Centre for Resource and Environmental Studies
The Australian National University
Canberra ACT 0200
Australia
T: +61 2 6125 7800 email: Simon.Blomberg_at_anu.edu.au
F: +61 2 6125 0757
CRICOS Provider # 00120C

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Received on Fri Jul 28 18:32:41 2006

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