[R] Using sample() with a data frame ?

[baptiste auguie]

Hi,

I find convenient to use a custom function for this:

sample.df <-
function (df, N = 1000, ...)
{
     df[sample(nrow(df), N, ...), ]
}


sample.df(daf1,1000)

Hope this helps,

baptiste


On 25 Aug 2008, at 12:31, Martin Hvidberg wrote:

>
>
> I have a data frame (daf1), that holds +80000 records, and 10  
> variables (i.e. 10 columns and some 80000 rows)
>
>> length(daf1)
> [1] 10
>> length(daf1[,1])
> [1] 83805
>
> I would like to sample() e.g. 10000 records from this. I use:
>
>> daf2 <- sample(daf1, 1000, replace = FALSE, prob = NULL)
> Error in `[.data.frame`(x, .Internal(sample(length(x), size,  
> replace,  :
>  cannot take a sample larger than the population when 'replace =  
> FALSE'
>
> As length(daf1) is 10, it thinks I'm taking 10000 samples from a  
> size 10 population... Arghhh
>
> How do I go about sampeling from a data frame?
>
> :-( Martin
>
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_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag