[R] Logical matrices
Spencer Graves
spencer.graves at pdf.com
Wed Nov 5 18:44:35 CET 2003
Please read 'help("|")': "|" performs elementwise comparison,
while "||" 'evaluates left to right examining only the first element of
each vector. Evaluation proceeds only until the result is determined.'
Consider the following:
> B <- cbind(diag(3), rep(0, 3), c(0,0,1))
> B[1,3] <- 1
> B[1,]|B[3,]
[1] TRUE FALSE TRUE FALSE TRUE
> B[1,]||B[3,]
[1] TRUE
hope this helps. spencer graves
Aurora Torrente wrote:
> Hello,
> I've been trying to work with 0-1 matrices as if they were logical,
> but using the logical operators doesn't produce what I need, for using
> the matrix B:
>
> [,1] [,2] [,3] [,4] [,5]
> [1,] 1 0 1 0 0
> [2,] 0 1 0 0 0
> [3,] 0 0 1 0 1
>
> gives me the following:
>
> > B[1,]<-B[1,] || B[3,]
>
> > B
> [,1] [,2] [,3] [,4] [,5]
> [1,] 1 1 1 1 1
> [2,] 0 1 0 0 0
> [3,] 0 0 1 0 1
>
> instead of :
>
> [,1] [,2] [,3] [,4] [,5]
> [1,] 1 0 1 0 1
> [2,] 0 1 0 0 0
> [3,] 0 0 1 0 1
>
> which is what I need.
> I've tried to convert it into a logical matrix, but the result was a
> vector:
>
> > C<-as.logical(B)
> > C
> [1] TRUE FALSE FALSE TRUE TRUE FALSE TRUE FALSE TRUE TRUE FALSE
> FALSE TRUE FALSE TRUE
>
> What could I do? Thanks for your help,
>
> Aurora
>
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