[R] sample {base}

[David Carlson]

Something like this?

> set.seed(42)
> a <- sample.int(10)
> b <- sample.int(5)
> c <- sample.int(3)
> smpl <- function(x) sample(x, ifelse(length(x)<5, length(x), 5))
> smpl(a)
[1]  4  8  1 10  2
> smpl(b)
[1] 2 3 5 1 4
> smpl(c)
[1] 2 1 3

-------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77840-4352





-----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of Xochitl CORMON
Sent: Wednesday, June 5, 2013 9:28 AM
To: r-help at r-project.org
Subject: [R] sample {base}

Hi all,

I'm trying to randomly select sample numbers for length class groups
(5 
per length class).

For this I'm using a loop FOR and the function sample () and
specified a 
size for the sampling of 5. Unfortunately, one of the length class
group 
does not contain 5 individuals. For me is not a big deal as I have 
others groups to complete. However it bothers me that the sampling 
function does not select any individuals in this group generating
the 
error below :

Error in sample(Gpool2$SampleNb[Gpool2$LngtClas == LngtClas[[i]] & 
Gpool2$SpCode ==  : can not take a sample larger than the population

when 'replace = FALSE'.

I understand why this error message appears but I was wondering if
there 
is a way to select all the items present in the group even if it's
not 5 
(something like size =< 5).

LngtClas <- list( "40_49", "50_59", "60_69", "70_")
SpCode <- list ("POLLVIR ", "MERLMER")

a <- as.character(sample(Gpool$SampleNb[Gpool$LngtClas ==
LngtClas[[4]] 
& Gpool$SpCode == SpCode[[2]]], size = 5, replace = FALSE))

You can find enclosed my dataset,

Thank you for the help,

Xochitl C.

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Xochitl CORMON
+33 (0)3 21 99 56 84

Doctorante en sciences halieutiques
PhD student in fishery sciences

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IFREMER
Centre Manche Mer du Nord
150 quai Gambetta
62200 Boulogne-sur-Mer

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