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

[Hervé Pagès]

On 06/08/2018 10:32 AM, Hervé Pagès wrote:
> On 06/08/2018 10:15 AM, Michael Lawrence wrote:
>> There probably should be an abstraction for this. In S4Vectors, we
>> have extractROWS().
> 
> FWIW the code in S4Vectors that does what your subset_ROW() does is:
> 
> 
> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_Bioconductor_S4Vectors_blob_04cc9516af986b30445e99fd1337f13321b7b4f6_R_subsetting-2Dutils.R-23L466-2DL476&d=DwIFaQ&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=LnDTzOeXwI6VI-4SVVi2rwDE7A-az-AhxPAB6X7Lkhc&s=_2PVGd2BrNNHtPjGsJkhSLAmtX3eoFuZDWWs2c8zZ4w&e= 

Wrong link sorry. Here is the correct one:

 
https://github.com/Bioconductor/S4Vectors/blob/04cc9516af986b30445e99fd1337f13321b7b4f6/R/subsetting-utils.R#L453-L464

H.

> 
> 
> (This is the default "extractROWS" method.)
> 
> Except for the normalization of 'i', it does the same as your
> subset_ROW(). I don't know how to do this without generating a call
> with missing arguments.
> 
> H.
> 
>>
>> Michael
>>
>> On Fri, 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?
>>>
>>> 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
>>>
>>> -- 
>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__hadley.nz&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=MF0DzYDiaYtcFXIyQwpQKs9lVbLNvdBBUubTv7BVAfM&s=GSpoAzc1Kn_BnTIkDh0HBFGKtRm-xFodxEPOejriC9Q&e= 
>>>
>>>
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>>
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>>
>>
> 

-- 
Hervé Pagès

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