[R] automatic coercicion

[Adams, Jean]

>From one Jean to another ... A[i, , drop=FALSE]

On Sat, Mar 21, 2015 at 6:04 AM, <Jean.Coursol at math.u-psud.fr> wrote:

> My question must be a trivial one.
>
> There is automatic coercicion to vector when extracting only one line of a
> matrix.
> # example
> A = matrix(1:12,3,4)
> rownames(A) = c('a1','a2','a3')
>
> i = 1:2
> A[i,]
> #    [,1] [,2] [,3] [,4]
> # a1    1    4    7   10    matrix
> # a2    2    5    8   11
>
> i = 1
> A[i,]
> # [1]  1  4  7 10           vector !!!
>
> # to get the rowname, it is necessary to do
> rownames(A)[i]
> # [1] "a1"
>
> Is it possible to get a (1,4)-matrix (without testing length(i) ) ? I see
> nothing in options()...
>
> Jean Coursol
>
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