From: Armstrong, Whit <whit.armstrong_at_hcmny.com>

Date: Fri 22 Sep 2006 - 18:39:48 GMT

+ }

[5,] 100 -0.9565273

attr(,"class")

[1] "foo"

R-help@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 and provide commented, minimal, self-contained, reproducible code. Received on Sat Sep 23 04:42:04 2006

Date: Fri 22 Sep 2006 - 18:39:48 GMT

Can someone help me understand the following behavior of "[<-" ?

If I define a simple class based on a matrix, the [<- operation only inserts into the first column:

> x <- matrix(rnorm(10),nrow=5,ncol=2) > class(x) <- "foo" > "[<-.foo" <- function(x, i, j, value) { + if(missing(i)) i <- 1:nrow(x) + if(missing(j)) j <- 1:ncol(x) + + x <- unclass(x) + x <- NextMethod(.Generic) + class(x) <- "foo" + x

+ }

> > x[] <- 100.0 > x [,1] [,2][4,] 100 -0.2886357

[1,] 100 -0.1465296[2,] 100 -0.2615796[3,] 100 -0.8882629

[5,] 100 -0.9565273

attr(,"class")

[1] "foo"

Based on the behavior of [<- for a matrix, I would have thought that the data for the whole object would be replaced.

for instance:

> y <- matrix(rnorm(10),nrow=5,ncol=2)

> y

[,1] [,2]

*[1,] -0.55297049 -1.1896488
**[2,] 0.06157438 -0.6628254
**[3,] -0.28184208 -2.5260177
*

[4,] 0.61204398 -0.3492488

[5,] 0.43971216 1.8990789

> y[] <- 100

> y

[,1] [,2]

*[1,] 100 100
**[2,] 100 100
**[3,] 100 100
*

[4,] 100 100

[5,] 100 100

>

Thanks,

Whit

code for above:

x <- matrix(rnorm(10),nrow=5,ncol=2)

x

class(x) <- "foo"

"[<-.foo" <- function(x, i, j, value) {

if(missing(i)) i <- 1:nrow(x)

if(missing(j)) j <- 1:ncol(x)

x <- unclass(x)

x <- NextMethod(.Generic)

class(x) <- "foo"

x

}

x[] <- 100.0

x

> R.Version()

$platform

[1] "i686-pc-linux-gnu"

$arch

[1] "i686"

$os

[1] "linux-gnu"

$system

[1] "i686, linux-gnu"

$status

[1] ""

$major

[1] "2"

$minor

[1] "3.1"

$year

[1] "2006"

$month

[1] "06"

$day

[1] "01"

$`svn rev`

[1] "38247"

$language

[1] "R"

$version.string

[1] "Version 2.3.1 (2006-06-01)"

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sat Sep 23 04:42:04 2006

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