Also the TRUEs cause problems if some dimensions are 0:
> matrix(raw(0), nrow=5, ncol=0)[1:3 , TRUE]
Error in matrix(raw(0), nrow = 5, ncol = 0)[1:3, TRUE] :
(subscript) logical subscript too long
H.
On 06/08/2018 10:29 AM, Hadley Wickham wrote:
I suspect this will have suboptimal performance since the TRUEs will
get recycled. (Maybe there is, or could be, ALTREP, support for
recycling)
Hadley
On Fri, Jun 8, 2018 at 10:16 AM, Berry, Charles <ccbe...@ucsd.edu> wrote:
On Jun 8, 2018, at 8:45 AM, Hadley Wickham <h.wick...@gmail.com> wrote:
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?
You can use TRUE to fill the subscripts for dimensions 2:nd
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 <-
function(x,i)
{
mc <- quote(x[i])
nd <- max(1L, length(dim(x)))
mc[seq(4, length=nd-1L)] <- rep(list(TRUE), nd - 1L)
mc[["drop"]] <- FALSE
eval(mc)
}
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
HTH,
Chuck
--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fredhutch.org
Phone: (206) 667-5791
Fax: (206) 667-1319
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