> On Dec 14, 2015, at 12:46 PM, David L Carlson <dcarl...@tamu.edu> wrote:
>
> There are lots of ways to do this. For example,
Another method with mapply:
mapply(function( n, vals) {sample(vals$id, n)} , # no replacement is the
default for sample
vals= split(data, findInterval(data$value, 0:5) )[1:5] , # drops
the values at 5 or above
n=c(10,7,5,5,3) )
$`1`
[1] 12 64 10 60 70 58 33 50 57 68
$`2`
[1] 43 8 15 26 19 3 20
$`3`
[1] 55 9 62 17 67
$`4`
[1] 61 21 31 24 48
$`5`
[1] 44 13 36
>
>> groups <- cut(data$value, include.lowest = T, right = FALSE,
> + breaks = 0:ceiling(max(data$value)))
>> grp <- c("[0,1)", "[1,2)", "[2,3)", "[3,4)", "[4,5)")
>> size <- c(10, 7, 5, 5, 3)
>> set.seed(42)
>> samples <- lapply(1:5, function(x) sample(data$id[groups==grp[x]],
> + size[x]))
>> names(samples) <- grp
>> samples
> $`[0,1)`
> [1] 69 68 33 63 56 46 65 12 50 58
>
> $`[1,2)`
> [1] 20 34 43 8 15 52 19
>
> $`[2,3)`
> [1] 7 22 62 28 2
>
> $`[3,4)`
> [1] 61 53 5 25 21
>
> $`[4,5)`
> [1] 59 35 40
>
>>
>> groups <- cut(data$value, include.lowest = T, right = FALSE,
> + breaks = 0:ceiling(max(data$value)))
>> grp <- c("[0,1)", "[1,2)", "[2,3)", "[3,4)", "[4,5)")
>> size <- c(10, 7, 5, 5, 3)
>> set.seed(42)
>> samples <- lapply(1:5, function(x) sample(data$id[groups==grp[x]],
> + size[x]))
>> names(samples) <- grp
>> samples
> $`[0,1)`
> [1] 69 68 33 63 56 46 65 12 50 58
>
> $`[1,2)`
> [1] 20 34 43 8 15 52 19
>
> $`[2,3)`
> [1] 7 22 62 28 2
>
> $`[3,4)`
> [1] 61 53 5 25 21
>
> $`[4,5)`
> [1] 59 35 40
>
>
> -------------------------------------
> David L Carlson
> Department of Anthropology
> Texas A&M University
> College Station, TX 77840-4352
>
>
>
> -----Original Message-----
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Frank S.
> Sent: Monday, December 14, 2015 2:02 PM
> To: r-help@r-project.org
> Subject: [R] Random selection of a fixed number of values by interval
>
> Dear R users,
>
> I'm writing to this list because I must get a random sample (without
> replacement) from a given vector, but the clue is that I need to extract a
> fixed number of values by each prespecified 1-unit interval. As an example I
> try to say, I have a data frame that looks like this (my real dataframe is
> bigger):
>
> data <- data.frame(id = 1:70, value= c(0.68, 2.96, 1.93, 5.63, 3.08, 3.10,
> 2.99, 1.79, 2.96, 0.85, 11.79, 0.06, 4.31, 0.64, 1.43, 0.88, 2.79, 4.67,
> 1.23, 1.43, 3.05, 2.44, 2.55, 3.82, 3.55, 1.56, 7.25, 2.75, 9.64, 5.14,
> 3.54, 3.12, 0.17, 1.07, 4.08, 4.47, 5.58, 7.41, 0.85, 4.30, 7.58,
> 0.58, 1.40, 4.74, 5.04, 0.14, 1.14, 3.28, 7.84, 0.07, 3.97, 1.02, 3.47,
> 0.66, 2.38, 0.06, 0.67, 0.48, 4.48, 0.12, 3.82, 2.27, 0.93, 0.30,
> 0.73, 0.33, 2.91, 0.81, 0.18, 0.42))
>
> And I would like to select, in a random manner:
>
> 10 id's whose value belongs to [0,1) interval
> 7 id's whose value belongs to [1,2)
> 5 id's whose value belongs to [2,3)
> 5 id's whose value belongs to [3,4)
> 3 id's whose value belongs to [4,5)
>
> # I have the following values by each 1-unit interval:
> table(cut(data$value, include.lowest = T, right = FALSE, breaks =
> 0:ceiling(max(data$value))))
>
> and the size vector:
> size <- c(10, 7, 5, 5, 3)
>
> But I'm not able to get it by using sample function. Does anyone have some
> idea?
>
> Thank you very much for any suggestions!!
>
> Frank S.
>
>
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
