[Rd] Subsetting the "ROW"s of an object

[Iñaki Úcar]

Sorry, without remnants from other attempts:

subset_ROW <- function(x, i) {
  nd <- length(dim(x))
  if (nd <= 1L)
    return(x[i])
  apply(x, 2:nd, `[`, i, drop=FALSE)
}
El vie., 8 jun. 2018 a las 19:07, Iñaki Úcar (<i.ucar86 using gmail.com>) escribió:
>
> El vie., 8 jun. 2018 a las 17:46, Hadley Wickham
> (<h.wickham using gmail.com>) escribió:
> >
> > Hi all,
> >
> > Is there a better to way to subset the ROWs (in the sense of NROW) of
> > an vector, matrix, data frame or array than this?
> >
> > subset_ROW <- function(x, i) {
> >   nd <- length(dim(x))
> >   if (nd <= 1L) {
> >     x[i]
> >   } else {
> >     dims <- rep(list(quote(expr = )), nd - 1L)
> >     do.call(`[`, c(list(quote(x), quote(i)), dims, list(drop = FALSE)))
> >   }
> > }
> >
> > subset_ROW(1:10, 4:6)
> > #> [1] 4 5 6
> >
> > str(subset_ROW(array(1:10, c(10)), 2:4))
> > #>  int [1:3(1d)] 2 3 4
> > str(subset_ROW(array(1:10, c(10, 1)), 2:4))
> > #>  int [1:3, 1] 2 3 4
> > str(subset_ROW(array(1:10, c(5, 2)), 2:4))
> > #>  int [1:3, 1:2] 2 3 4 7 8 9
> > str(subset_ROW(array(1:10, c(10, 1, 1)), 2:4))
> > #>  int [1:3, 1, 1] 2 3 4
> >
> > subset_ROW(data.frame(x = 1:10, y = 10:1), 2:4)
> > #>   x y
> > #> 2 2 9
> > #> 3 3 8
> > #> 4 4 7
> >
> > It seems like there should be a way to do this that doesn't require
> > generating a call with missing arguments, but I can't think of it.
>
> The following code seems to work. The only minor drawback is that, for
> the last case, the output is not a data frame.
>
> subset_ROW <- function(x, i) {
>   nd <- length(dim(x))
>   if (nd <= 1L)
>     return(x[i])
>   xx <- apply(x, 2:nd, `[`, i, drop=FALSE)
>   dim(xx) <- c(length(i), dim(x)[-1])
>   xx
> }
>
> Iñaki
>
> >
> > Thanks!
> >
> > Hadley
> >
> > --
> > http://hadley.nz
> >



-- 
Iñaki Úcar
http://www.enchufa2.es
@Enchufa2