RE: [R] Getting elements of a matrix by a vector of column indice s
See if the following helps:
m - outer(letters[1:5], 1:4, paste, sep=)
m
[,1] [,2] [,3] [,4]
[1,] a1 a2 a3 a4
[2,] b1 b2 b3 b4
[3,] c1 c2 c3 c4
[4,] d1 d2 d3 d4
[5,] e1 e2 e3 e4
idx - c(2, 1, 3, 4, 2)
m[cbind(1:5, idx)]
[1] a2 b1 c3 d4 e2
Andy
From: Wolfram Fischer
I have e.g.
t - matrix( nrow=2, ncol=3, byrow=TRUE,
c('a1','a2','a3','b1','b2','b3') )
and
i - c( 3, 2)
Is it possible to formulate a simple expression that gets
c( t[ 1, i[1] ], t[ 2, i[2] ] )
(and so on for longer matrices)?
The result would be:
[1] a3 b2
Thanks - Wolfram
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Re: [R] Getting elements of a matrix by a vector of column indice s
Thanks for you answer! It works.
m - outer(letters[1:5], 1:4, paste, sep=)
The following works with the help of your proposition:
rowidx.n - c( 2, 3, 4)
colidx.n - c( 1, 3, 2)
idx.n - cbind( rowidx.n, colidx.n )
m[idx.n]
[1] b1 c3 d2
In my real data there was an additional difficulty:
I had names of rows and columns as indices:
rownames(m) - paste('R', 1:nrow(m), sep=)
colnames(m) - paste('C', 1:ncol(m), sep= )
And the following did not work anymore:
rowidx - c( 'R2', 'R3', 'R4' )
colidx - c( 'C1', 'C3', 'C2' )
idx - cbind( rowidx, colidx )
m[idx]
NA NA NA NA NA NA
NA NA NA NA NA NA
Do you have another suggestion? - Thanks! Wolfram
--- In reply to: ---
Date:08.07.04 08:21 (-0400)
From:Liaw, Andy [EMAIL PROTECTED]
Subject: RE: [R] Getting elements of a matrix by a vector of column indice s
See if the following helps:
m - outer(letters[1:5], 1:4, paste, sep=)
m
[,1] [,2] [,3] [,4]
[1,] a1 a2 a3 a4
[2,] b1 b2 b3 b4
[3,] c1 c2 c3 c4
[4,] d1 d2 d3 d4
[5,] e1 e2 e3 e4
idx - c(2, 1, 3, 4, 2)
m[cbind(1:5, idx)]
[1] a2 b1 c3 d4 e2
Andy
From: Wolfram Fischer
I have e.g.
t - matrix( nrow=2, ncol=3, byrow=TRUE,
c('a1','a2','a3','b1','b2','b3') )
and
i - c( 3, 2)
Is it possible to formulate a simple expression that gets
c( t[ 1, i[1] ], t[ 2, i[2] ] )
(and so on for longer matrices)?
The result would be:
[1] a3 b2
Thanks - Wolfram
__
[EMAIL PROTECTED] mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
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RE: [R] Getting elements of a matrix by a vector of column indice s
This should work:
idx - cbind(match(rowidx, rownames(m)), match(colidx, colnames(m)))
m[idx]
[1] b1 c3 d2
Andy
From: Wolfram Fischer
Thanks for you answer! It works.
m - outer(letters[1:5], 1:4, paste, sep=)
The following works with the help of your proposition:
rowidx.n - c( 2, 3, 4)
colidx.n - c( 1, 3, 2)
idx.n - cbind( rowidx.n, colidx.n )
m[idx.n]
[1] b1 c3 d2
In my real data there was an additional difficulty:
I had names of rows and columns as indices:
rownames(m) - paste('R', 1:nrow(m), sep=)
colnames(m) - paste('C', 1:ncol(m), sep= )
And the following did not work anymore:
rowidx - c( 'R2', 'R3', 'R4' )
colidx - c( 'C1', 'C3', 'C2' )
idx - cbind( rowidx, colidx )
m[idx]
NA NA NA NA NA NA
NA NA NA NA NA NA
Do you have another suggestion? - Thanks! Wolfram
--- In reply to: ---
Date:08.07.04 08:21 (-0400)
From:Liaw, Andy [EMAIL PROTECTED]
Subject: RE: [R] Getting elements of a matrix by a vector of
column indice s
See if the following helps:
m - outer(letters[1:5], 1:4, paste, sep=)
m
[,1] [,2] [,3] [,4]
[1,] a1 a2 a3 a4
[2,] b1 b2 b3 b4
[3,] c1 c2 c3 c4
[4,] d1 d2 d3 d4
[5,] e1 e2 e3 e4
idx - c(2, 1, 3, 4, 2)
m[cbind(1:5, idx)]
[1] a2 b1 c3 d4 e2
Andy
From: Wolfram Fischer
I have e.g.
t - matrix( nrow=2, ncol=3, byrow=TRUE,
c('a1','a2','a3','b1','b2','b3') )
and
i - c( 3, 2)
Is it possible to formulate a simple expression that gets
c( t[ 1, i[1] ], t[ 2, i[2] ] )
(and so on for longer matrices)?
The result would be:
[1] a3 b2
Thanks - Wolfram
__
[EMAIL PROTECTED] mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
--
Notice: This e-mail message, together with any
attachments, contains information of Merck Co., Inc. (One
Merck Drive, Whitehouse Station, New Jersey, USA 08889),
and/or its affiliates (which may be known outside the United
States as Merck Frosst, Merck Sharp Dohme or MSD and in
Japan, as Banyu) that may be confidential, proprietary
copyrighted and/or legally privileged. It is intended solely
for the use of the individual or entity named on this
message. If you are not the intended recipient, and have
received this message in error, please notify us immediately
by reply e-mail and then delete it from your system.
--
__
[EMAIL PROTECTED] mailing list
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PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
