About matrix manipulation

An embedded and charset-unspecified text was scrubbed...
Name: not available
URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20120821/e623397b/attachment.pl>
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 Gon?alves-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.

	[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.