R help - Apr 2005 - indexing an array using an index-array, but one entry being ', '

in the specific example you could consider something like this:

test <- array(c(1:16), dim = c(3,4,3))
##
test.ind <- rbind(c(2,4,1), c(2,4,2), c(2,4,3))
test[test.ind]
test[2,4,]

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.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Christoph Lehmann" <christoph.lehmann at gmx.ch>
To: <R-help at stat.math.ethz.ch>
Sent: Tuesday, April 19, 2005 3:11 PM
Subject: [R] indexing an array using an index-array, but one entry 
being ', '

> Hi
> I have the following array:
>
> test <- array(c(1:16), dim = c(3,4,3))
> test
> ## I call some enries using an index array
> test.ind <- array(rbind(c(1,2,1), c(3,3,2)), dim = c(2,3))
> test[test.ind]
>
> ## suppose I want all values in the 2nd row and 4th col over
> ## all three 3rd dimensions
> test[2,4,]
>
>
> how to specify a test.ind array with the last index left with ',' 
> i.e
> test.ind should be evaluated as "2, 4, , " so that it can be
> calledlike above as test[test.ind] and the
> result should be [1] 11  7  3
>
> thanks for a hint
> Cheers
> christoph
>
> ______________________________________________
> 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
>

Hi
I have the following array:

test <- array(c(1:16), dim = c(3,4,3))
test
## I call some enries using an index array
test.ind <- array(rbind(c(1,2,1), c(3,3,2)), dim = c(2,3))
test[test.ind]

## suppose I want all values in the 2nd row and 4th col over
## all three 3rd dimensions
test[2,4,]


how to specify a test.ind array with the last index left with ',' i.e
test.ind should be evaluated as "2, 4, , " so that it can be
calledlike above as test[test.ind] and the
result should be [1] 11  7  3

thanks for a hint
Cheers
christoph

OK, the hint by Dimitris applied I just do very simple:


test <- array(c(1:16), dim = c(3,4,3))
test
## I call some enries using an index array
test.ind <- array(rbind(c(1,2,1), c(3,3,2)), dim = c(2,3))
test[test.ind]

## suppose I want all values in the 2nd row and 4th col over
## all three 3rd dimensions
test[2,4,]

## using an index array
nn <- dim(test)[3]
voxel.ind <- c(2, 4)
test.ind <- array(cbind(rep(voxel.ind[1], nn), rep(voxel.ind[2], nn), 
1:nn), dim = c(nn, 3))

test[test.ind]

cheers
christoph
Christoph Lehmann wrote:
> Hi
> I have the following array:
> 
> test <- array(c(1:16), dim = c(3,4,3))
> test
> ## I call some enries using an index array
> test.ind <- array(rbind(c(1,2,1), c(3,3,2)), dim = c(2,3))
> test[test.ind]
> 
> ## suppose I want all values in the 2nd row and 4th col over
> ## all three 3rd dimensions
> test[2,4,]
> 
> 
> how to specify a test.ind array with the last index left with ','
i.e
> test.ind should be evaluated as "2, 4, , " so that it can be
> calledlike above as test[test.ind] and the
> result should be [1] 11  7  3
> 
> thanks for a hint
> Cheers
> christoph
> 
> ______________________________________________
> 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
> 
>