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Re: extracting elements
From: |
Mike Miller |
Subject: |
Re: extracting elements |
Date: |
Sun, 1 May 2005 10:59:20 -0500 (CDT) |
On Sat, 30 Apr 2005, Steve C. Thompson wrote:
How about this:
I=[1,2,5,4]'; % desired rows
J=[1,3;2,4;1,4;2,3]; % desired columns
X=reshape([1:20],4,5)'; % matrix to pull elements from
X1=X';
[Jr,Jc]=size(J);
[X1r,X1c]=size(X1);
a=(I-1)*X1r*ones(1,Jc);
Y=X1(J+a)
Thanks, Steve! Is that the same as this?:
X(I*ones(1,size(J,2))+size(X,1)*(J-1))
It took me awhile, but that's what I came up with.
Let's see...
size(X,1)=X1c
size(J,2)=Jc
X(I*ones(1,Jc)+X1c*(J-1))
Well, it's hard to figure out. Your use of the transpose is throwing me
off. If they both give the same answer, that's good enough for me!
Thanks again.
Mike
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