Ask for help: find corresponding elements between matrix

Hi,

I guess this is what you wanted:
seq1<-matrix(c(1,-1,0,1,1,-1,0,0,-1,1,1,NA),3,4)
seq1
#???? [,1] [,2] [,3] [,4]
#[1,]??? 1??? 1??? 0??? 1
#[2,]?? -1??? 1??? 0??? 1
#[3,]??? 0?? -1?? -1?? NA

set.seed(15)
mat1<-matrix(rnorm(12),3)


?mat1
#?????????? [,1]?????? [,2]?????? [,3]?????? [,4]
#[1,]? 0.2588229? 0.8971982? 0.0227882 -1.0750013
#[2,]? 1.8311207? 0.4880163? 1.0907732? 0.8550108
#[3,] -0.3396186 -1.2553858 -0.1321224 -0.3649801


? m<-sapply(seq_len(ncol(mat1)),function(i) ifelse(seq1[,i]==1|seq1[,i]==-1,mat1[,i],NA))
?m
#????????? [,1]?????? [,2]?????? [,3]?????? [,4]
#[1,] 0.2588229? 0.8971982???????? NA -1.0750013
#[2,] 1.8311207? 0.4880163???????? NA? 0.8550108
#[3,]??????? NA -1.2553858 -0.1321224???????? NA
A.K.

----- Original Message -----
From: JiangZhengyu <zhyjiang2006 at hotmail.com>
To: r-help at r-project.org
Cc: 
Sent: Thursday, February 21, 2013 9:39 AM
Subject: [R] Ask for help: find corresponding elements between matrix











Dear R experts,

I have two matrix (seq & mat) & I want to retrieve in a new matrix all the numbers from mat that =1 (corresponding to the same row/ column position) in seq, or all the numbers in mat that =-1 in seq. - Replace all the numbers with NA if it's not 1/-1 in seq.? There are some "NA"s in seq. 

seq=matrix(c(1,-1,0,1,1,-1,0,0,-1,1,1,NA),3,4)
mat=matrix(rnorm(12),3)
I made this code but I don't know where's the problem..

seq=matrix(c(1,-1,0,1,1,-1,0,0,-1,1,1,NA),3,4)
mat=matrix(rnorm(12),3)

m=rep(NA,nrow(seq))
for(i in 1:nrow(seq))
{m[i]=mat[seq[i]==1]
}


Error in m[i] = mat[seq[i] == 1] : replacement has length zero
In addition: Warning message:
In m[i] = mat[seq[i] == 1] :
? number of items to replace is not a multiple of replacement length

I was wondering if anyone can help me with this.
Thanks in advance, 
Zhengyu
eg. here is what I want

head(seq)

? ?  [,1] [,2] [,3] [,4]
[1,]? ? 1? ? 1? ? 0? ? 1
[2,]?  -1? ? 1? ? 0? ? 1
[3,]? ? 0?  -1?  -1?  NA

head(mat)

? ? ? ? ?  [,1]? ? ?  [,2]? ? ?  [,3]? ? ? [,4]
[1,]? 0.1006950? 0.3354360? 0.1796888 1.3198761
[2,]? 1.0948252? 0.5350797 -0.5739454 0.2744478
[3,] -0.5409936 -0.3820084 -0.5601096 0.9239680

This is a new new matrix.

head(mat1)

? ? ? ? ?  [,1]? ? ?  [,2]? ? ?  [,3]? ? ? [,4]
[1,]? 0.1006950? 0.3354360? NA 1.3198761
[2,]? NA? 0.5350797 NA 0.2744478
[3,]? NA NA NA NA

??? ???  ??? ?  ??? ??? ?  ??? ???  ??? ?  ??? ??? ?  ??? ???  ??? ?  ??? ??? ? 
??? [[alternative HTML version deleted]]

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