On 19/07/2013 10:17 AM, Kátia Emidio wrote:
Hi,
I am a beginner at R and I would like to get information from a matrix,
where the numbers are larger than or equal to 50m . This means that plants
need to be apart at least 50m. I need to get the selection as in a way
that I can identify which pair of species are 50m or more apart.
here a peace of my matrix:
Nauc_calo_1 Nauc_calo_2 Nauc_calo_3 Nauc_calo_1 0 22 36 Nauc_calo_2 22
0 165.8 Nauc_calo_3 36 165.8 0
The which() function with arr.ind=TRUE will identify which matrix
entries meet a condition. For example,
> M <- matrix(rnorm(20), 4, 5)
> M
[,1] [,2] [,3] [,4] [,5]
[1,] -0.6947070 1.2079620 0.77996512 -0.04287046 -1.5487528
[2,] -0.2079173 -1.1231086 -0.08336907 1.36860228 0.5846137
[3,] -1.2653964 -0.4028848 0.25331851 -0.22577099 0.1238542
[4,] 2.1689560 -0.4666554 -0.02854676 1.51647060 0.2159416
> which(M > 1.5, arr.ind=TRUE)
row col
[1,] 4 1
[2,] 4 4
Duncan Murdoch
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