[R] r data structures

[R. Michael Weylandt]

On Thu, Aug 16, 2012 at 5:44 PM, MacQueen, Don <macqueen1 at llnl.gov> wrote:
> Whereas for a matrix or data frame, one must supply *two* index values
> (even if one of them may be omitted)
>   mydf[ 1 , 3 ]
>   mydf[   , 5 ]
>
>   mymat[ 2:5 ,     ]
>   mymat[ 3   , 4:6 ]
> are valid statements.
>

Not quite:

x <- matrix(rev(1:9), ncol = 3)

x[5]

x[2:6]

x <- data.frame(x)

x[3]

I understand this as meaning, when you don't use special 2D indexing,
R falls back on 1D indexing behavior given by the relevant superclass:
vector for matrix and list for data.frame.

Cheers,
RMW