Crispin Miller wrote:
> Hi,
> I've got a quick question about what happens when indexing into matrices
> with a single column. I was wondering if anyone can help ...
>
> For example:
>
>>x <- matrix(1:10)
>
>
>>y <- cbind(x,x)
>
>
>>x[4:6,]
>
>
> [1] 4 5 6
>
>
>>y[4:6,]
>
>
> [,1] [,2]
>
> [1,] 4 4
>
> [2,] 5 5
>
> [3,] 6 6
>
>
>>class(x[4:6,])
>
>
> [1] "integer"
>
>
>>class(y[4:6,])
>
>
> [1] "matrix"
>
> It seems that R is returning the results of indexing into a matrix with
> one column as a vector rather than a matrix?
>
> Does anyone have a good way of preventing this from happening?
Yes, the argument "drop":
x[4:6,,drop=FALSE]
Uwe Ligges
> cheers,
>
> crispin
>
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