This is a guess since you didn't say where it comes from.
It looks like a data.frame where some rows were deleted.
Also, note that the column names in your example are sorted alphabetically
instead of numerically.  This example shows one way to get that behavior.

Rich


> tmp <- data.frame(matrix(1:24, 6, 4, dimnames=list(1:6, c(1,2,11,12))))
> tmp
  X1 X2 X11 X12
1  1  7  13  19
2  2  8  14  20
3  3  9  15  21
4  4 10  16  22
5  5 11  17  23
6  6 12  18  24
> dimnames(tmp)[[2]] <- sort(dimnames(tmp)[[2]])
> tmp
  X1 X11 X12 X2
1  1   7  13 19
2  2   8  14 20
3  3   9  15 21
4  4  10  16 22
5  5  11  17 23
6  6  12  18 24
> tmp[c(2,5,3),]
  X1 X11 X12 X2
2  2   8  14 20
5  5  11  17 23
3  3   9  15 21
>
On Wed, Jun 2, 2010 at 5:47 PM, Changbin Du <changbind@gmail.com> wrote:

> > dim(tmp)
> [1] 576  12
> > tmp
>
>       1 10 11 12 13  2  3  4  5  6  7  9
>  1    0  0  0  0  0  0  0 12  0  0  0  0
>  2    0  0  0  0  0  0  0 15  0  0  0  0
>

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