R help - Oct 2006 - matrix multiplication

Dear all,

I have 2 matrices, one is a 8x3 matrix, called X; the other matrix is a 3x3
indicator matrix with the diagonal element as 0 or 1. when a variable is
included in the model, the corresponding diagonal element is 1, otherwise, it is
0.  Let A be a set of matrices that contain the possible indicator matrix. e.g.,
A= [A1, A2, A3], 
where A1= [1,0,0;0,0,0,0,0,0],
A2 =[1,0,0;0,1,0,0,0,0], 
A3 =[1,0,0;0,0,0,0,1,0]

In order to derive the new X matries depending on the indicator matrices, I use
for loops to multiply both X and A as following

p<-3
for ( i in 1:p){
          XX<- X%*%A[i]
        }

However, it only shows the result when i=p. How can I derive the results which
include all possible value of XX[i], i=1,..,p, rather than just i=p

thanks for any help

Ya-Hsiu



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Is this what you want ?

 > A1<-matrix(c(1,0,0,0,0,0,0,0,0),3)
 > A2<-matrix(c(1,0,0,0,1,0,0,0,0),3)
 > A3<-matrix(c(1,0,0,0,1,0,0,1,0),3)
 > X <- matrix(1:24,8)
 > XX<-list()
 > for(i in 1:3){
+ XX[[i]]<-X%*%A[[i]]
+ }
 > XX
[[1]]
     [,1] [,2] [,3]
[1,]    1    0    0
[2,]    2    0    0
[3,]    3    0    0
[4,]    4    0    0
[5,]    5    0    0
[6,]    6    0    0
[7,]    7    0    0
[8,]    8    0    0

[[2]]
     [,1] [,2] [,3]
[1,]    1    9    0
[2,]    2   10    0
[3,]    3   11    0
[4,]    4   12    0
[5,]    5   13    0
[6,]    6   14    0
[7,]    7   15    0
[8,]    8   16    0

[[3]]
     [,1] [,2] [,3]
[1,]    1    9    9
[2,]    2   10   10
[3,]    3   11   11
[4,]    4   12   12
[5,]    5   13   13
[6,]    6   14   14
[7,]    7   15   15
[8,]    8   16   16

 >



Ya-Hsiu Chuang wrote:
>Dear all,
>
>I have 2 matrices, one is a 8x3 matrix, called X; the other matrix is a 3x3
indicator matrix with the diagonal element as 0 or 1. when a variable is
included in the model, the corresponding diagonal element is 1, otherwise, it is
0.  Let A be a set of matrices that contain the possible indicator matrix. e.g.,
>A= [A1, A2, A3], 
>where A1= [1,0,0;0,0,0,0,0,0],
>A2 =[1,0,0;0,1,0,0,0,0], 
>A3 =[1,0,0;0,0,0,0,1,0]
>
>In order to derive the new X matries depending on the indicator matrices, I
use for loops to multiply both X and A as following
>
>p<-3
>for ( i in 1:p){
>          XX<- X%*%A[i]
>        }
>
>However, it only shows the result when i=p. How can I derive the results
which include all possible value of XX[i], i=1,..,p, rather than just i=p
>
>thanks for any help
>
>Ya-Hsiu
>
>
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help@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
>and provide commented, minimal, self-contained, reproducible code.
>
>  
>

-- 
Ferdinand Alimadhi
Programmer / Analyst
Harvard University
The Institute for Quantitative Social Science
(617) 496-0187
falimadhi@iq.harvard.edu
www.iq.harvard.edu


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