Re: [R] problem applying a conditional formula to each element of a matrix

From: jim holtman <jholtman_at_gmail.com>
Date: Wed, 12 Dec 2007 14:50:45 -0800

I think you want to use 'ifelse':

> Cov.f <- function(h, sigmasq, phi) {

+ ifelse(h <= phi, sigmasq * (1 - ( 1.5 * (h/phi) - 0.5 * (h/phi)^3)), 0) + }
>
> x.coord <- c(5.7, 6.7, 9.8)
> y.coord <- c(42.7, 10.2, 77.4)
> coords <- cbind(x.coord, y.coord)
> distance.matrix <- as.matrix(dist(coords, method="euclidean"))
> distance.matrix

         1 2 3

1  0.00000 32.51538 34.94138
2 32.51538  0.00000 67.27146
3 34.94138 67.27146  0.00000

> Cov.f(distance.matrix, 3.9, 58.1)
1 2 3 1 3.9000000 0.9678766 0.8059627

2 0.9678766 3.9000000 0.0000000
3 0.8059627 0.0000000 3.9000000
>

On Dec 12, 2007 1:35 PM, Dale Steele <dale.w.steele_at_gmail.com> wrote:
> I'm applying a function (Cov.f) defined below to each element of a
> distance matrix. When I run the code below, I get a warning message
> (below) and elements of returned matrix [2,3] and [3,2] are not zero
> as I would expect. Clearly, there is an error... What am I doing
> wrong? Thanks. --Dale
>
> Warning message:
> In if (h <= phi) { :
> the condition has length > 1 and only the first element will be used
>
> # function
>
> Cov.f <- function(h, sigmasq, phi) {
> if (h <= phi) {Cij <- sigmasq * (1 - ( 1.5 * (h/phi) - 0.5 *
> (h/phi)^3)) } else
> if (h > phi) {Cij <- 0}
> return(Cij)
> }
>
> x.coord <- c(5.7, 6.7, 9.8)
> y.coord <- c(42.7, 10.2, 77.4)
> coords <- cbind(x.coord, y.coord)
> distance.matrix <- as.matrix(dist(coords, method="euclidean"))
> distance.matrix
> Cov.f(distance.matrix, 3.9, 58.1)
>
> ______________________________________________
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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.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

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Received on Wed 12 Dec 2007 - 22:58:11 GMT

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