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 <zhyjiang2...@hotmail.com>
To: r-help@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
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and provide commented, minimal, self-contained, reproducible code.
