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package sampling, function strata
2 messages · Elena Guijarro, Thomas Lumley
On Wed, Feb 1, 2012 at 11:18 PM, Elena Guijarro
<elena.guijarro at vi.ieo.es> wrote:
Dear all,
I have to select 122 stratified random samples from a population of
?>3900 cells. I have 41 strata and I ?have to draw a different number of
samples from them(between 2 and 8).
I have tried to apply the funtion strata following the instruction in
the manual:
strata(dataframe, stratanames=NULL, size, method=c("srswor"),
pik,description=TRUE)
but I get the error message
Error in data.frame((1:nrow(data))[srswor(size, nrow(data)) == 1], rep(size/nrow(data), ?:
? arguments imply differing number of rows: 3, 122
My stratanames and size vectors have the same length, 41 (the number of strata), and 122 is the number of samples I need. The size vector is sorted in the order the strata have in the dataframe (dim 3960 8).
You specified stratanames=NULL, which is not documented to work, and doesn't seem to work on examples I tried.
names(dataframe) [1] "lond" ? ? ? ?"latd" ? ? ? ?"stratanames" "cell" ? ? ? ?"lat" ? ? ? ? "lon" ? ? ? ? "div" ? ? ? ? "ID_unit"
Try specifying stratanames="stratanames", which is what the documentation and examples seem to imply. -thomas
Thomas Lumley Professor of Biostatistics University of Auckland