R devel - Jan 2011 - str() on raster objects fails for certain dimensions

Hi,

str() on raster objects fails for certain dimensions.  For example:
> str(as.raster(0, nrow=1, ncol=100))
 'raster' chr [1, 1:100] "#000000" "#000000"
"#000000" "#000000" ...
> str(as.raster(0, nrow=1, ncol=101))
Error in `[.raster`(object, seq_len(max.len)) : subscript out of bounds

This seems to do with how str() and "[.raster"() is coded; when
subsetting as a vector, which str() relies on, "[.raster"() still
returns a matrix-like object, e.g.
> img <- as.raster(1:25, max=25, nrow=5, ncol=5);
> img[1:2]
     [,1]      [,2]      [,3]      [,4]      [,5]
[1,] "#0A0A0A" "#3D3D3D" "#707070"
"#A3A3A3" "#D6D6D6"
[2,] "#141414" "#474747" "#7A7A7A"
"#ADADAD" "#E0E0E0"

compare with:
> as.matrix(img)[1:2]
[1] "#0A0A0A" "#3D3D3D"


The easy but incomplete fix is to do:

str.raster <- function(object, ...) {
  str(as.matrix(object), ...);
}

Other suggestions?

> sessionInfo()
R version 2.13.0 Under development (unstable) (2011-01-27 r54129)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):

/Henrik

>>>>> Henrik Bengtsson <hb at biostat.ucsf.edu>
>>>>>     on Mon, 31 Jan 2011 11:16:59 -0800 writes:
    > Hi, str() on raster objects fails for certain dimensions.  For
    > example:

    >> str(as.raster(0, nrow=1, ncol=100)) 'raster' chr [1, 1:100]
    > "#000000" "#000000" "#000000"
"#000000" ...

    >> str(as.raster(0, nrow=1, ncol=101)) Error in `[.raster`(object,
    > seq_len(max.len)) : subscript out of bounds

    > This seems to do with how str() and "[.raster"() is coded;
when
    > subsetting as a vector, which str() relies on, "[.raster"()
    > still returns a matrix-like object, e.g.

    >> img <- as.raster(1:25, max=25, nrow=5, ncol=5);
    >> img[1:2]
    > [,1]      [,2]      [,3]      [,4]      [,5]
    > [1,] "#0A0A0A" "#3D3D3D" "#707070"
"#A3A3A3" "#D6D6D6"
    > [2,] "#141414" "#474747" "#7A7A7A"
"#ADADAD" "#E0E0E0"

    > compare with:

    >> as.matrix(img)[1:2]
    > [1] "#0A0A0A" "#3D3D3D"


    > The easy but incomplete fix is to do:

    > str.raster <- function(object, ...) {
    > str(as.matrix(object), ...);
    > }

    > Other suggestions?

The informal "raster" class is behaving ``illogical''
in the following sense:

 > r <- as.raster(0, nrow=1, ncol=11)
 > r[seq_along(r)]
 Error in `[.raster`(r, seq_along(r)) : subscript out of bounds

or, here equivalently,
 > r[1:length(r)]
 Error in `[.raster`(r, 1:length(r)) : subscript out of bounds

When classes do behave in such a way, they definitely need their
own str() method.

However, the bug really is in "[.raster":
Currently,  r[i] is equivalent to  r[i,]  which is not at all 
matrix-like and its help clearly says that subsetting should
work as for matrices.
A recent thread on R-help/R-devel has mentioned the fact that
"[" methods for matrix-like methods need to use both nargs() and
missing() and that "[.dataframe" has been the example to follow
"forever", IIRC already in S and S-plus as of 20 years ago.

Thank you, Henrik, for the bug report.
Martin