[R] Trouble creating and adjacency matrix

Spartina lea_olsen at yahoo.ca
Sun Sep 25 23:07:17 CEST 2011


Hello all,

I'm having trouble creating an adjacency matrix. 

Basically, I need to turn the following distance matrix into an adjacency
matrix based on whether values are >1.5 or not. If they are >1.5, then the
returned value should be 0. If they are =<1.5, then the returned value
should be 1.

DistanceMatrix:

           A             B          C             D          E
[1,] 0.000000 2.828427 1.581139 2.236068 2.000000
[2,] 2.828427 0.000000 1.581139 4.123106 2.000000
[3,] 1.581139 1.581139 0.000000 2.549510 2.121320
[4,] 2.236068 4.123106 2.549510 0.000000 4.123106
[5,] 2.000000 2.000000 2.121320 4.123106 0.000000

I'm trying to do this via the if statement, however I can't get it to work
and it keeps returning an error message:

> if(DistanceMatrix>1.5) {0} else {1}
[1] 1
Warning message:
In if (DistanceMatrix > 1.5) { :
the condition has length > 1 and only the first element will be used


I am brand new to R and have a very limited knowledge of functions and
syntax. Maybe the if statement is not even the right way of tackling this
problem....

Thanks in advance for your answers!

Léa

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