[R] Re shape matrix from wide to long format

Dieter Menne dieter.menne at menne-biomed.de
Tue Nov 25 14:09:09 CET 2008




Daren Tan wrote:
> 
> 
> I forgot the reshape equivalent for converting from wide to long format.
> Can someone help as my matrix is very big. The following is just an
> example. 
> 
>> m <- matrix(1:20, nrow=4, dimnames=list(LETTERS[1:4], letters[1:5]))
> 

Gabor's solution is uses more basic functions, but package reshape or 
function reshape(...direction="long") would also work


library(reshape)
m <- matrix(1:20, nrow=4, dimnames=list(LETTERS[1:4], letters[1:5])) 
mdf = cbind(V1=rownames(m),as.data.frame(m))
melt(mdf)


Dieter



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