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From: wapo on 10 Sep 2009 10:15
Nice solution. Now lets make it a bit more difficult. What if I have
the following:

a=rand(3,3,10);
b=eye(3);
ind=[1 3 5];
for i=1:10
c(ind)=a(:,:,i).*b
end

So now I want the three diagonal elements in the slice to be placed in
specific locations on the new matrix. This fails cause a(:,:,i).*b is
3*3 whereas logical indexing expects 3 elements.

Any ideas???
From: Matt on 10 Sep 2009 11:28
wapo <apostolos1975(a)gmail.com> wrote in message <3ff7a906-f6f9-4246-8679-7467799d7f2d(a)t2g2000yqn.googlegroups.com>...

> > Perhaps as follows:
> >
> > aa=reshape(a,9,[]);
> > c=aa([1 5 9],:),
>
> I was hoping to avoid copying data around and read them directly from
> the original matrix.


There is no data copying involved here. The variable "aa" points to the exact same copy of the data as does "a".
From: Matt on 10 Sep 2009 11:32
wapo <apostolos1975(a)gmail.com> wrote in message <37bd5376-1ea6-46f3-813c-edc2419b801c(a)s39g2000yqj.googlegroups.com>...
> Nice solution. Now lets make it a bit more difficult. What if I have
> the following:
>
> a=rand(3,3,10);
> b=eye(3);
> ind=[1 3 5];
> for i=1:10
> c(ind)=a(:,:,i).*b
> end
>
> So now I want the three diagonal elements in the slice to be placed in
> specific locations on the new matrix. This fails cause a(:,:,i).*b is
> 3*3 whereas logical indexing expects 3 elements.

The following is a simple modification to what I had before, and again involves no copying of the data in "a"

aa=reshape(a,9,[]);
c(ind,:)=aa([1 5 9],:),
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