[R] how to do something like " subset(mat, ("col1">4 & "col2">4)) "

[Andy Bunn]

Some thing like this?

mat <- matrix(1:9,3,3)
mat
mat[apply(mat[,2:3] > 4,1,all),]
# or less cryptically
foo <- mat[,2:3] > 4
bar <- apply(foo,1,all)
mat[bar,]

HTH, Andy

NB: No need to send this kind of message to r-devel


> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Florence Combes
> Sent: Friday, September 09, 2005 10:09 AM
> To: r-help at stat.math.ethz.ch; r-devel-request at stat.math.ethz.ch
> Subject: [R] how to do something like " subset(mat, ("col1">4 &
> "col2">4)) "
> 
> 
> Dear all, 
> 
> I have a problem with the "subset()" function. I spent all day yesterday 
> with a collegue to solve it and we did not find a satisfying 
> solution (even 
> in the archived mails), so I ask for your help. 
> Let's say (for a simple example) a matrix mat: 
> 
> R> mat
> cola colb colc
> [1,] 1 4 7
> [2,] 2 5 8
> [3,] 3 6 9
> 
> My goal is to select the lines of the matrix on the basis of the 
> values of 
> more than one column (let's say colb and colc). 
> For example I want to select all the lines of the matrix for 
> which values in 
> colb and colc are more than 4. 
> 
> I tried several ways that did not work: 
> 
> R> mat2 <- subset(mat, ("colb">4 & "colc">4))
> R> mat2
> [1] 1 2 3 4 5 6 7 8 9
> 
> it is a vector, not a matrix. 
> 
> > mat2 <- subset(mat, mat[,2:3]>4)
> > mat2
> [1] 2 3 4 5 6 8 9
> 
> tha same: it is a vector; so I tried: 
> 
> > mat2 <- as.matrix(subset(mat, mat[,("colb">4 & "colc">4)]))
> > mat2
> [,1]
> [1,] 1
> [2,] 2
> [3,] 3
> [4,] 4
> [5,] 5
> [6,] 6
> [7,] 7
> [8,] 8
> [9,] 9
> 
> not good :(
> 
> Did someone have an idea of how to select the only the lines 2 
> and 3 of mat 
> by a selection on "colb" and "colc" >4 ? 
> 
> Thanks a lot, 
> 
> Florence. 
> 
> Version 2.0.1 (2004-11-15)
> (Linux Debian).
> 
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> 
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