Hello,
Try the following.
library(reshape2)
# Don't need 'cbind'
mat <- data.frame(sp1=c(rep(0, 5), rep(1, 5)),
sp2=sample(c(rep(0, 6),rep(1, 4))),
fac=c(rep("a", 3), rep("b", 3), rep("c", 4)))
mat.new <- matrix (c(0, 1, 1, 1, 1, 1), nrow=2, ncol=3)
rownames(mat.new) <- c("sp1", "sp2")
colnames(mat.new) <- c("a", "b", "c")
m <- melt(mat, id.vars = "fac")
result <- xtabs(value ~ variable + fac, data = m)
result <- apply(result, 2, function(x) ifelse(x == 0, 0, 1))
Hope this helps,
Rui Barradas
Em 21-08-2012 20:29, Thiago Gonçalves-Souza escreveu:
Dear list,
I'm trying to create a matrix by combining the sites that species occur in
a new matrix with species as rows and sites as columns.
The main matrix is "mat":
mat <- as.data.frame(cbind(sp1=c(rep(0, 5), rep(1, 5)),sp2=sample(c(rep(0,
6),rep(1, 4))),
fac=c(rep("a", 3), rep("b", 3),rep("c", 4))))
The first two columns are species and the third one is the site that
species occur (value 1) or not (value 0).
The resulting matrix ("mat.new") should be like this one:
mat.new <- matrix (c(0, 1, 1, 1, 1, 1), nrow=2, ncol=3)
rownames(mat.new) <- c("sp1", "sp2")
colnames(mat.new) <- c("a", "b", "c")
mat.new
So, species are now the rownames and sites are colnames and the values
within this matrix are the presence/absence of each species. I've tried
aggregate, tapply, sapply functions but I wasn't able to re-create that
matrix.
Thanks in advance,
Thiago.
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