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.
Thanks!
Hadley
--
http://hadley.nz
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