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Subsetting the "ROW"s of an object

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hadley wickham

Subsetting the "ROW"s of an object

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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Iñaki Úcar

Re: Subsetting the "ROW"s of an object

El vie., 8 jun. 2018 a las 17:46, Hadley Wickham
(<[hidden email]>) 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
>

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Iñaki Úcar

Re: Subsetting the "ROW"s of an object

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 (<[hidden email]>) escribió:

>
> El vie., 8 jun. 2018 a las 17:46, Hadley Wickham
> (<[hidden email]>) 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

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Michael Lawrence-3

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

There probably should be an abstraction for this. In S4Vectors, we
have extractROWS().

Michael

On Fri, Jun 8, 2018 at 8:45 AM, Hadley Wickham <[hidden email]> 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
>
> --
> http://hadley.nz
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

______________________________________________
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Berry, Charles

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

> On Jun 8, 2018, at 8:45 AM, Hadley Wickham <[hidden email]> 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

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hadley wickham

Re: Subsetting the "ROW"s of an object

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 <[hidden email]> wrote:

>
>
>> On Jun 8, 2018, at 8:45 AM, Hadley Wickham <[hidden email]> 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
>

--
http://hadley.nz

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Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

In reply to this post by Michael Lawrence-3

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://github.com/Bioconductor/S4Vectors/blob/04cc9516af986b30445e99fd1337f13321b7b4f6/R/subsetting-utils.R#L466-L476

(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 <[hidden email]> 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=
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=MF0DzYDiaYtcFXIyQwpQKs9lVbLNvdBBUubTv7BVAfM&s=HsEbNAT5IElAUS-W2VVSeJs4tfQc77heV7BbQxru518&e=
>>
>
> ______________________________________________
> [hidden email] mailing list
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=MF0DzYDiaYtcFXIyQwpQKs9lVbLNvdBBUubTv7BVAfM&s=HsEbNAT5IElAUS-W2VVSeJs4tfQc77heV7BbQxru518&e=
>

--
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: [hidden email]
Phone: (206) 667-5791
Fax: (206) 667-1319

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Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

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 <[hidden email]>
>> 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=
>>>
>>>
>>> ______________________________________________
>>> [hidden email] mailing list
>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=MF0DzYDiaYtcFXIyQwpQKs9lVbLNvdBBUubTv7BVAfM&s=HsEbNAT5IElAUS-W2VVSeJs4tfQc77heV7BbQxru518&e=
>>>
>>>
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Ddevel&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=MF0DzYDiaYtcFXIyQwpQKs9lVbLNvdBBUubTv7BVAfM&s=HsEbNAT5IElAUS-W2VVSeJs4tfQc77heV7BbQxru518&e=
>>
>>
>

Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

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 <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 8:45 AM, Hadley Wickham <[hidden email]> 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
>>
>
>
>

Berry, Charles

Re: Subsetting the "ROW"s of an object

> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>
> 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

OK. But this is easy enough to handle.

>
> 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

AFAICS, it is not an issue. Taking

arr <- array(rnorm(2^22),c(2^10,4,4,4))

as a test case

and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':

subset_ROW4 <-
function(x, i, useLiteral=FALSE)
{
literal <- quote(x[i,,,,drop=FALSE])
mc <- quote(x[i])
nd <- max(1L, length(dim(x)))
mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
mc[["drop"]] <- FALSE
if (useLiteral)
eval(literal)
else
eval(mc)
}

I get identical times with

system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))

and with

system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))

Changing the dimensions to c(2^5, 2^7, 4, 4 ) and running something similar also shows equal times.

Chuck

>> On Fri, Jun 8, 2018 at 10:16 AM, Berry, Charles <[hidden email]> wrote:
>>>
>>>
>>>> On Jun 8, 2018, at 8:45 AM, Hadley Wickham <[hidden email]> 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: [hidden email]
> Phone: (206) 667-5791
> Fax: (206) 667-1319

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hadley wickham

Re: Subsetting the "ROW"s of an object

On Fri, Jun 8, 2018 at 11:38 AM, Berry, Charles <[hidden email]> wrote:

>
>
>> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>>
>> 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
>
> OK. But this is easy enough to handle.
>
>>
>> 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
>
>
> AFAICS, it is not an issue. Taking
>
> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>
> as a test case
>
> and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':
>
> subset_ROW4 <-
> function(x, i, useLiteral=FALSE)
> {
> literal <- quote(x[i,,,,drop=FALSE])
> mc <- quote(x[i])
> nd <- max(1L, length(dim(x)))
> mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
> mc[["drop"]] <- FALSE
> if (useLiteral)
> eval(literal)
> else
> eval(mc)
> }
>
> I get identical times with
>
> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))
>
> and with
>
> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))

I think that's because you used a relatively low precision timing
mechnaism, and included the index generation in the timing. I see:

arr <- array(rnorm(2^22),c(2^10,4,4,4))
i <- seq(1,length = 10, by = 100)

bench::mark(
arr[i, TRUE, TRUE, TRUE],
arr[i, , , ]
)
#> # A tibble: 2 x 1
#> expression min mean median max n_gc
#> <chr> <bch:t> <bch:t> <bch:tm> <bch:tm> <dbl>
#> 1 arr[i, TRUE,… 7.4µs 10.9µs 10.66µs 1.22ms 2
#> 2 arr[i, , , ] 7.06µs 8.8µs 7.85µs 538.09µs 2

So not a huge difference, but it's there.

Hadley

--
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Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

A missing subscript is still preferable to a TRUE though because it
carries the meaning "take it all". A TRUE also achieves this but via
implicit recycling. For example x[ , , ] and x[TRUE, TRUE, TRUE]
achieve the same thing (if length(x) != 0) and are both no-ops but
the subsetting code gets a chance to immediately and easily detect
the former as a no-op whereas it will probably not be able to do it
so easily for the latter. So in this case it will most likely generate
a copy of 'x' and fill the new array by taking a full walk on it.

H.

On 06/08/2018 11:52 AM, Hadley Wickham wrote:

> On Fri, Jun 8, 2018 at 11:38 AM, Berry, Charles <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>>>
>>> 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
>>
>> OK. But this is easy enough to handle.
>>
>>>
>>> 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
>>
>>
>> AFAICS, it is not an issue. Taking
>>
>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>
>> as a test case
>>
>> and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':
>>
>> subset_ROW4 <-
>> function(x, i, useLiteral=FALSE)
>> {
>> literal <- quote(x[i,,,,drop=FALSE])
>> mc <- quote(x[i])
>> nd <- max(1L, length(dim(x)))
>> mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
>> mc[["drop"]] <- FALSE
>> if (useLiteral)
>> eval(literal)
>> else
>> eval(mc)
>> }
>>
>> I get identical times with
>>
>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))
>>
>> and with
>>
>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))
>
> I think that's because you used a relatively low precision timing
> mechnaism, and included the index generation in the timing. I see:
>
> arr <- array(rnorm(2^22),c(2^10,4,4,4))
> i <- seq(1,length = 10, by = 100)
>
> bench::mark(
> arr[i, TRUE, TRUE, TRUE],
> arr[i, , , ]
> )
> #> # A tibble: 2 x 1
> #> expression min mean median max n_gc
> #> <chr> <bch:t> <bch:t> <bch:tm> <bch:tm> <dbl>
> #> 1 arr[i, TRUE,… 7.4µs 10.9µs 10.66µs 1.22ms 2
> #> 2 arr[i, , , ] 7.06µs 8.8µs 7.85µs 538.09µs 2
>
> So not a huge difference, but it's there.
>
> Hadley
>
>

Berry, Charles

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

> On Jun 8, 2018, at 11:52 AM, Hadley Wickham <[hidden email]> wrote:
>
> On Fri, Jun 8, 2018 at 11:38 AM, Berry, Charles <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>>>
>>> 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
>>
>> OK. But this is easy enough to handle.
>>
>>>
>>> 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
>>
>>
>> AFAICS, it is not an issue. Taking
>>
>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>
>> as a test case
>>
>> and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':
>>
>> subset_ROW4 <-
>> function(x, i, useLiteral=FALSE)
>> {
>> literal <- quote(x[i,,,,drop=FALSE])
>> mc <- quote(x[i])
>> nd <- max(1L, length(dim(x)))
>> mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
>> mc[["drop"]] <- FALSE
>> if (useLiteral)
>> eval(literal)
>> else
>> eval(mc)
>> }
>>
>> I get identical times with
>>
>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))
>>
>> and with
>>
>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))
>
> I think that's because you used a relatively low precision timing
> mechnaism, and included the index generation in the timing. I see:
>
> arr <- array(rnorm(2^22),c(2^10,4,4,4))
> i <- seq(1,length = 10, by = 100)
>
> bench::mark(
> arr[i, TRUE, TRUE, TRUE],
> arr[i, , , ]
> )
> #> # A tibble: 2 x 1
> #> expression min mean median max n_gc
> #> <chr> <bch:t> <bch:t> <bch:tm> <bch:tm> <dbl>
> #> 1 arr[i, TRUE,… 7.4µs 10.9µs 10.66µs 1.22ms 2
> #> 2 arr[i, , , ] 7.06µs 8.8µs 7.85µs 538.09µs 2
>
> So not a huge difference, but it's there.

Funny. I get similar results to yours above albeit with smaller differences. Usually < 5 percent.

But with subset_ROW4 I see no consistent difference.

In this example, it runs faster on average using `eval(mc)' to return the result:

> arr <- array(rnorm(2^22),c(2^10,4,4,4))
> i <- seq(1,length=10,by=100)
> bench::mark(subset_ROW4(arr,i,FALSE), subset_ROW4(arr,i,TRUE))[,1:8]
# A tibble: 2 x 8
expression min mean median max `itr/sec` mem_alloc n_gc
<chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm> <dbl> <bch:byt> <dbl>
1 subset_ROW4(arr, i, FALSE) 28.9µs 34.9µs 32.1µs 1.36ms 28686. 5.05KB 5
2 subset_ROW4(arr, i, TRUE) 28.9µs 35µs 32.4µs 875.11µs 28572. 5.05KB 5
>

And on subsequent reps the lead switches back and forth.

Chuck

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hadley wickham

Re: Subsetting the "ROW"s of an object

Hmmm, yes, there must be some special case in the C code to avoid
recycling a length-1 logical vector:

dims <- c(4, 4, 4, 1e5)

arr <- array(rnorm(prod(dims)), dims)
dim(arr)
#> [1] 4 4 4 100000
i <- c(1, 3)

bench::mark(
arr[i, TRUE, TRUE, TRUE],
arr[i, , , ]
)[c("expression", "min", "mean", "max")]
#> # A tibble: 2 x 4
#> expression min mean max
#> <chr> <bch:tm> <bch:tm> <bch:tm>
#> 1 arr[i, TRUE, TRUE, TRUE] 41.8ms 43.6ms 46.5ms
#> 2 arr[i, , , ] 41.7ms 43.1ms 46.3ms

On Fri, Jun 8, 2018 at 12:31 PM, Berry, Charles <[hidden email]> wrote:

>
>
>> On Jun 8, 2018, at 11:52 AM, Hadley Wickham <[hidden email]> wrote:
>>
>> On Fri, Jun 8, 2018 at 11:38 AM, Berry, Charles <[hidden email]> wrote:
>>>
>>>
>>>> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>>>>
>>>> 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
>>>
>>> OK. But this is easy enough to handle.
>>>
>>>>
>>>> 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
>>>
>>>
>>> AFAICS, it is not an issue. Taking
>>>
>>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>>
>>> as a test case
>>>
>>> and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':
>>>
>>> subset_ROW4 <-
>>> function(x, i, useLiteral=FALSE)
>>> {
>>> literal <- quote(x[i,,,,drop=FALSE])
>>> mc <- quote(x[i])
>>> nd <- max(1L, length(dim(x)))
>>> mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
>>> mc[["drop"]] <- FALSE
>>> if (useLiteral)
>>> eval(literal)
>>> else
>>> eval(mc)
>>> }
>>>
>>> I get identical times with
>>>
>>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))
>>>
>>> and with
>>>
>>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))
>>
>> I think that's because you used a relatively low precision timing
>> mechnaism, and included the index generation in the timing. I see:
>>
>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>> i <- seq(1,length = 10, by = 100)
>>
>> bench::mark(
>> arr[i, TRUE, TRUE, TRUE],
>> arr[i, , , ]
>> )
>> #> # A tibble: 2 x 1
>> #> expression min mean median max n_gc
>> #> <chr> <bch:t> <bch:t> <bch:tm> <bch:tm> <dbl>
>> #> 1 arr[i, TRUE,… 7.4µs 10.9µs 10.66µs 1.22ms 2
>> #> 2 arr[i, , , ] 7.06µs 8.8µs 7.85µs 538.09µs 2
>>
>> So not a huge difference, but it's there.
>
>
> Funny. I get similar results to yours above albeit with smaller differences. Usually < 5 percent.
>
> But with subset_ROW4 I see no consistent difference.
>
> In this example, it runs faster on average using `eval(mc)' to return the result:
>
>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>> i <- seq(1,length=10,by=100)
>> bench::mark(subset_ROW4(arr,i,FALSE), subset_ROW4(arr,i,TRUE))[,1:8]
> # A tibble: 2 x 8
> expression min mean median max `itr/sec` mem_alloc n_gc
> <chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm> <dbl> <bch:byt> <dbl>
> 1 subset_ROW4(arr, i, FALSE) 28.9µs 34.9µs 32.1µs 1.36ms 28686. 5.05KB 5
> 2 subset_ROW4(arr, i, TRUE) 28.9µs 35µs 32.4µs 875.11µs 28572. 5.05KB 5
>>
>
> And on subsequent reps the lead switches back and forth.
>
>
> Chuck
>

--
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Michael Lawrence-3

Re: Subsetting the "ROW"s of an object

Actually, it's sort of the opposite. Everything becomes a sequence of
integers internally, even when the argument is missing. So the same
amount of work is done, basically. ALTREP will let us improve this
sort of thing.

Michael

On Fri, Jun 8, 2018 at 1:49 PM, Hadley Wickham <[hidden email]> wrote:

> Hmmm, yes, there must be some special case in the C code to avoid
> recycling a length-1 logical vector:
>
> dims <- c(4, 4, 4, 1e5)
>
> arr <- array(rnorm(prod(dims)), dims)
> dim(arr)
> #> [1] 4 4 4 100000
> i <- c(1, 3)
>
> bench::mark(
> arr[i, TRUE, TRUE, TRUE],
> arr[i, , , ]
> )[c("expression", "min", "mean", "max")]
> #> # A tibble: 2 x 4
> #> expression min mean max
> #> <chr> <bch:tm> <bch:tm> <bch:tm>
> #> 1 arr[i, TRUE, TRUE, TRUE] 41.8ms 43.6ms 46.5ms
> #> 2 arr[i, , , ] 41.7ms 43.1ms 46.3ms
>
>
> On Fri, Jun 8, 2018 at 12:31 PM, Berry, Charles <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 11:52 AM, Hadley Wickham <[hidden email]> wrote:
>>>
>>> On Fri, Jun 8, 2018 at 11:38 AM, Berry, Charles <[hidden email]> wrote:
>>>>
>>>>
>>>>> On Jun 8, 2018, at 10:37 AM, Hervé Pagès <[hidden email]> wrote:
>>>>>
>>>>> 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
>>>>
>>>> OK. But this is easy enough to handle.
>>>>
>>>>>
>>>>> 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
>>>>
>>>>
>>>> AFAICS, it is not an issue. Taking
>>>>
>>>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>>>
>>>> as a test case
>>>>
>>>> and using a function that will either use the literal code `x[i,,,,drop=FALSE]' or `eval(mc)':
>>>>
>>>> subset_ROW4 <-
>>>> function(x, i, useLiteral=FALSE)
>>>> {
>>>> literal <- quote(x[i,,,,drop=FALSE])
>>>> mc <- quote(x[i])
>>>> nd <- max(1L, length(dim(x)))
>>>> mc[seq(4,length=nd-1L)] <- rep(TRUE, nd-1L)
>>>> mc[["drop"]] <- FALSE
>>>> if (useLiteral)
>>>> eval(literal)
>>>> else
>>>> eval(mc)
>>>> }
>>>>
>>>> I get identical times with
>>>>
>>>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),TRUE))
>>>>
>>>> and with
>>>>
>>>> system.time(for (i in 1:10000) subset_ROW4(arr,seq(1,length=10,by=100),FALSE))
>>>
>>> I think that's because you used a relatively low precision timing
>>> mechnaism, and included the index generation in the timing. I see:
>>>
>>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>> i <- seq(1,length = 10, by = 100)
>>>
>>> bench::mark(
>>> arr[i, TRUE, TRUE, TRUE],
>>> arr[i, , , ]
>>> )
>>> #> # A tibble: 2 x 1
>>> #> expression min mean median max n_gc
>>> #> <chr> <bch:t> <bch:t> <bch:tm> <bch:tm> <dbl>
>>> #> 1 arr[i, TRUE,… 7.4µs 10.9µs 10.66µs 1.22ms 2
>>> #> 2 arr[i, , , ] 7.06µs 8.8µs 7.85µs 538.09µs 2
>>>
>>> So not a huge difference, but it's there.
>>
>>
>> Funny. I get similar results to yours above albeit with smaller differences. Usually < 5 percent.
>>
>> But with subset_ROW4 I see no consistent difference.
>>
>> In this example, it runs faster on average using `eval(mc)' to return the result:
>>
>>> arr <- array(rnorm(2^22),c(2^10,4,4,4))
>>> i <- seq(1,length=10,by=100)
>>> bench::mark(subset_ROW4(arr,i,FALSE), subset_ROW4(arr,i,TRUE))[,1:8]
>> # A tibble: 2 x 8
>> expression min mean median max `itr/sec` mem_alloc n_gc
>> <chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm> <dbl> <bch:byt> <dbl>
>> 1 subset_ROW4(arr, i, FALSE) 28.9µs 34.9µs 32.1µs 1.36ms 28686. 5.05KB 5
>> 2 subset_ROW4(arr, i, TRUE) 28.9µs 35µs 32.4µs 875.11µs 28572. 5.05KB 5
>>>
>>
>> And on subsequent reps the lead switches back and forth.
>>
>>
>> Chuck
>>
>
>
>
> --
> http://hadley.nz
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

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Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

The C code for subsetting doesn't need to recycle a logical subscript.
It only needs to walk on it and start again at the beginning of the
vector when it reaches the end. Not exactly the same as detecting the
"take everything along that dimension" situation though.
x[TRUE, TRUE, TRUE] triggers the full subsetting machinery when x[]
and x[ , , ] could (and should) easily avoid it.

H.

On 06/08/2018 01:49 PM, Hadley Wickham wrote:

Berry, Charles

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

> On Jun 8, 2018, at 1:49 PM, Hadley Wickham <[hidden email]> wrote:
>
> Hmmm, yes, there must be some special case in the C code to avoid
> recycling a length-1 logical vector:

Here is a version that (I think) handles Herve's issue of arrays having one or more 0 dimensions.

subset_ROW <-
function(x,i)
{
dims <- dim(x)
index_list <- which(dims[-1] != 0L) + 3
mc <- quote(x[i])
nd <- max(1L, length(dims))
mc[ index_list ] <- list(TRUE)
mc[[ nd + 3L ]] <- FALSE
names( mc )[ nd+3L ] <- "drop"
eval(mc)
}

Curiously enough the timing is *much* better for this implementation than for the first version I sent.

Constructing a version of `mc' that looks like `x[i,,,,drop=FALSE]' can be done with `alist(a=)' in place of `list(TRUE)' in the earlier version but seems to slow things down noticeably. It requires almost twice (!!) as much time as the version above.

Best,

Chuck
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hadley wickham

Re: Subsetting the "ROW"s of an object

On Fri, Jun 8, 2018 at 2:09 PM, Berry, Charles <[hidden email]> wrote:

>
>
>> On Jun 8, 2018, at 1:49 PM, Hadley Wickham <[hidden email]> wrote:
>>
>> Hmmm, yes, there must be some special case in the C code to avoid
>> recycling a length-1 logical vector:
>
>
> Here is a version that (I think) handles Herve's issue of arrays having one or more 0 dimensions.
>
> subset_ROW <-
> function(x,i)
> {
> dims <- dim(x)
> index_list <- which(dims[-1] != 0L) + 3
> mc <- quote(x[i])
> nd <- max(1L, length(dims))
> mc[ index_list ] <- list(TRUE)
> mc[[ nd + 3L ]] <- FALSE
> names( mc )[ nd+3L ] <- "drop"
> eval(mc)
> }
>
> Curiously enough the timing is *much* better for this implementation than for the first version I sent.
>
> Constructing a version of `mc' that looks like `x[i,,,,drop=FALSE]' can be done with `alist(a=)' in place of `list(TRUE)' in the earlier version but seems to slow things down noticeably. It requires almost twice (!!) as much time as the version above.

I think that's probably because alist() is a slow way to generate a
missing symbol:

bench::mark(
alist(x = ),
list(x = quote(expr = )),
check = FALSE
)[1:5]
#> # A tibble: 2 x 5
#> expression min mean median max
#> <chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm>
#> 1 alist(x = ) 2.8µs 3.54µs 3.29µs 34.9µs
#> 2 list(x = quote(expr = )) 169ns 219.38ns 181ns 24.2µs

(note the units)

Hadley

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Berry, Charles

Re: Subsetting the "ROW"s of an object

> On Jun 8, 2018, at 2:15 PM, Hadley Wickham <[hidden email]> wrote:
>
> On Fri, Jun 8, 2018 at 2:09 PM, Berry, Charles <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 1:49 PM, Hadley Wickham <[hidden email]> wrote:
>>>
>>> Hmmm, yes, there must be some special case in the C code to avoid
>>> recycling a length-1 logical vector:
>>
>>
>> Here is a version that (I think) handles Herve's issue of arrays having one or more 0 dimensions.
>>
>> subset_ROW <-
>> function(x,i)
>> {
>> dims <- dim(x)
>> index_list <- which(dims[-1] != 0L) + 3
>> mc <- quote(x[i])
>> nd <- max(1L, length(dims))
>> mc[ index_list ] <- list(TRUE)
>> mc[[ nd + 3L ]] <- FALSE
>> names( mc )[ nd+3L ] <- "drop"
>> eval(mc)
>> }
>>
>> Curiously enough the timing is *much* better for this implementation than for the first version I sent.
>>
>> Constructing a version of `mc' that looks like `x[i,,,,drop=FALSE]' can be done with `alist(a=)' in place of `list(TRUE)' in the earlier version but seems to slow things down noticeably. It requires almost twice (!!) as much time as the version above.
>
> I think that's probably because alist() is a slow way to generate a
> missing symbol:
>
> bench::mark(
> alist(x = ),
> list(x = quote(expr = )),
> check = FALSE
> )[1:5]
> #> # A tibble: 2 x 5
> #> expression min mean median max
> #> <chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm>
> #> 1 alist(x = ) 2.8µs 3.54µs 3.29µs 34.9µs
> #> 2 list(x = quote(expr = )) 169ns 219.38ns 181ns 24.2µs
>
> (note the units)

Yes. That is good for about half the difference. And I guess the rest is getting rid of seq(). This seems a bit quicker than anything else and satisfies Herve's objections:

subset_ROW <-
function(x,i)
{
dims <- dim(x)
nd <- length(dims)
index_list <- if (nd > 1) 2L + 2L:nd else 0
mc <- quote(x[i])
mc[ index_list ] <- list(quote(expr=))
mc[[ "drop" ]] <- FALSE
eval(mc)
}

Chuck
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Hervé Pagès-2

Re: Subsetting the "ROW"s of an object

In reply to this post by hadley wickham

On 06/08/2018 02:15 PM, Hadley Wickham wrote:

> On Fri, Jun 8, 2018 at 2:09 PM, Berry, Charles <[hidden email]> wrote:
>>
>>
>>> On Jun 8, 2018, at 1:49 PM, Hadley Wickham <[hidden email]> wrote:
>>>
>>> Hmmm, yes, there must be some special case in the C code to avoid
>>> recycling a length-1 logical vector:
>>
>>
>> Here is a version that (I think) handles Herve's issue of arrays having one or more 0 dimensions.
>>
>> subset_ROW <-
>> function(x,i)
>> {
>> dims <- dim(x)
>> index_list <- which(dims[-1] != 0L) + 3
>> mc <- quote(x[i])
>> nd <- max(1L, length(dims))
>> mc[ index_list ] <- list(TRUE)
>> mc[[ nd + 3L ]] <- FALSE
>> names( mc )[ nd+3L ] <- "drop"
>> eval(mc)
>> }
>>
>> Curiously enough the timing is *much* better for this implementation than for the first version I sent.
>>
>> Constructing a version of `mc' that looks like `x[i,,,,drop=FALSE]' can be done with `alist(a=)' in place of `list(TRUE)' in the earlier version but seems to slow things down noticeably. It requires almost twice (!!) as much time as the version above.
>
> I think that's probably because alist() is a slow way to generate a
> missing symbol:
>
> bench::mark(
> alist(x = ),
> list(x = quote(expr = )),
> check = FALSE
> )[1:5]
> #> # A tibble: 2 x 5
> #> expression min mean median max
> #> <chr> <bch:tm> <bch:tm> <bch:tm> <bch:tm>
> #> 1 alist(x = ) 2.8µs 3.54µs 3.29µs 34.9µs
> #> 2 list(x = quote(expr = )) 169ns 219.38ns 181ns 24.2µs
>
> (note the units)

That's a good one. Need to change this in S4Vectors::default_extractROWS()
and other places. Thanks!

H.

>
> Hadley
>
>

--
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: [hidden email]
Phone: (206) 667-5791
Fax: (206) 667-1319

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