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Topic: How to remove variable number of rows in each column of a matrix
Replies: 6   Last Post: Nov 3, 2013 1:14 AM

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bijan.mobasseri@gmail.com

Posts: 38
Registered: 7/19/05
Re: How to remove variable number of rows in each column of a matrix
Posted: Nov 3, 2013 1:14 AM
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On Saturday, November 2, 2013 8:37:09 AM UTC-4, Bruno Luong wrote:
> bijan.mobasseri@gmail.com wrote in message <211f42c1-8ebc-4716-bf45-35fd3cbb0e18@googlegroups.com>...
>

> > Say I have a 1000x10 matrix. The top of the matrix contains noisy data that I want to cut out. From column one I'd like to remove 10 values, from column 2, 15 values, from column 3, 8 values etc. After each column is reduced, I will keep the next 500 entries. So the end matrix will be 500x10. Right now I am doing it one column at a time which I have to put back together. Very tedious.
>
>
>
> % Dummy data for test
>
> A=rand(1000,10);
>
> idxstart=[10 15 8 7 29 14 1 72 4 4]; % index of the start row for each column
>
>
>
> [m n]=size(A);
>
> B = A(bsxfun(@plus, (0:n-1)*m + idxstart, (0:499)'));
>
>
>
> % Bruno


Bruno,

I have no idea what you are doing but it works! In case some may wonder where the application is, each column is a signal tract where the lead values are noise and need to be cut out. The problem is that the lead in segment has variable length, hence the question.



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