On 06/15/2012 08:13 AM, Peter Houk wrote:
Greetings -
I have a question regarding a relatively simple data transformation, and
wondering if it can be automated in R (or any other platform). For large
input datasets with numeric density and size, is there a function that can
reformat the data into a single vector for statistical analyses?
For instance, for the two column dataset:
numeric density size 5 5 4 8 3 9 4 10
How could the following output vector be automated:
size 5 5 5 5 5 8 8 8 8 9 9 9 10 10 10 10
mat=matrix(c(5,5,4,8,3,9,4,10), ncol=2, byrow=T)
rep(mat[,2], mat[,1])
Last, what if there was a third column for 'location', and the desired
output would be a single vector for each location?
mat2=matrix(c(5,5,1, 4,8,1, 3,9,2, 4,103, ), ncol=3, byrow=T)
by(mat2, list(factor(mat2[,3])), function(A) rep(A[,2], A[,1]) )
And use str() to check the by() object and extract what you want.
Bob
--
Bob O'Hara
Biodiversity and Climate Research Centre
Senckenberganlage 25
D-60325 Frankfurt am Main,
Germany
Tel: +49 69 798 40226
Mobile: +49 1515 888 5440
WWW: http://www.bik-f.de/root/index.php?page_id=219
Blog: http://blogs.nature.com/boboh
Journal of Negative Results - EEB: www.jnr-eeb.org
