[R] How to extract rows from matrices consistently?

[Wacek Kusnierczyk]

Feng, Ken wrote:
> Hi,
>
> How do I ensure that I always get a matrix back when I extract rows?
>
> The mickey-mouse example doesn't matter much, but if instead of 1:2 or
> 1, I have a vector which may have 1 or more values, then I'm in trouble.
>
> Any way to make this consistently return a matrix?
> Thx in advance.
>
> - Ken
>
> #
> ------------------------------------------------------------------------
> -------------------------
>
>   
>> x <- matrix( 1:10, nrow = 5 )
>> x
>>     
>      [,1] [,2]
> [1,]    1    6
> [2,]    2    7
> [3,]    3    8
> [4,]    4    9
> [5,]    5   10
>   
>> class( x[1:2,] )
>>     
> [1] "matrix"			# this is good
>   
>> class( x[1,] )
>>     
> [1] "integer"			# this is EVIL
>   


class(x[1,,drop=FALSE])

[1] "matrix"  # this is good (should be the default, perhaps)

vQ