From: Gabor Grothendieck <ggrothendieck_at_gmail.com>

Date: Fri 22 Sep 2006 - 18:59:49 GMT

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 05:04:36 2006

Date: Fri 22 Sep 2006 - 18:59:49 GMT

Try this:

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

class(x) <- "foo"

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

x <- unclass(x)

x <- NextMethod()

class(x) <- "foo"

x

}

x[] <- 100.0

On 9/22/06, Armstrong, Whit <whit.armstrong@hcmny.com> wrote:

> 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]
**> [1,] 100 -0.1465296
**> [2,] 100 -0.2615796
**> [3,] 100 -0.8882629
**> [4,] 100 -0.2886357
**> [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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**>
**>
**> ______________________________________________
**> 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.
**>
**>
**>
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