Hello,
Something like this?
different <- function(x, y) x == 1 & y == 0
set.seed(7054)
mat <- matrix(sample(0:1, 500, TRUE), nrow = 5)
rownames(mat) <- LETTERS[1:5]
colnames(mat) <- sprintf("D%03d", 1:100)
different(mat["B",], mat["E",])
Hope this helps,
Rui Barradas
Em 27-09-2013 11:48, Elaine Kuo escreveu:
Dear List,
I want to compare the presence and absence of bird species based on the
sites in a matrix.
The matrix has 5 rows for Island A, B, C, D, and E.
It has 100 columns for bird species D001-D100.
In each cell of the matrix,
the presence-absence of bird species will be recorded as 1 or 0.
(For example, if species D001 is found on Island D,
the matrix cell of species D001 and Island D will be 1.)
Now I want to know the different bird species between Island B and E.
In other words, I would like to find out bird species present (1) on Island
B but absent (0)on island E, and vice versa (absent (0) on Island B but
present (1)on island E).
Please kindly advise how to code the purpose above.
Thank you in advance.
Elaine
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