[Rd] Subsetting the "ROW"s of an object
Hervé Pagès
hp@ge@ @ending from fredhutch@org
Fri Jun 8 19:37:15 CEST 2018
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 <ccberry using ucsd.edu> wrote:
>>
>>
>>> On Jun 8, 2018, at 8:45 AM, Hadley Wickham <h.wickham using 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: hpages using fredhutch.org
Phone: (206) 667-5791
Fax: (206) 667-1319
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