R help - Sep 2005 - 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).

	[[alternative HTML version deleted]]

Florence Combes <fcombes at gmail.com> writes:
> 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 ? 

Well, subset has methods for vectors and data frames, so what happens
for matrices is basically that they get converted to vectors. I don't
know what gave you the idea of quoting the names, but 

"colb">4

is TRUE because numbers sort before letters!

Try something like

as.matrix(subset(as.data.frame(mat),colb>4 & colc>4))


-- 
   O__  ---- Peter Dalgaard             ??ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907

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).
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
http://www.R-project.org/posting-guide.html

maybe something like this:

subset(mat, mat[, 2] > 4 & mat[, 3] > 4)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Florence Combes" <fcombes at gmail.com>
To: <r-help at stat.math.ethz.ch>; <r-devel-request at
stat.math.ethz.ch>
Sent: Friday, September 09, 2005 4:09 PM
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).
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm