Keeping rows of a matrix between two indicies.

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Jason on 1 Feb 2018
Commented: Jason on 1 Feb 2018
Hi. I want to remove all rows from a matrix below idx1 and above idx2. that is I only want to keep rows that are between idx1 and idx2.
I have used this to do the 1st part:
C2(1:idx1,:) = []; %Trim the first rows upto idx1
But can't quite work out how to include removing above idx2 as the indexes will have changed now the above removal has occurred?
Thanks

Birdman on 1 Feb 2018
Edited: Birdman on 1 Feb 2018
One approach:
A=randi([1 5],15,5);%demo data
idx2=3;idx1=8;
A=A(idx2:idx1,:)

Jason on 1 Feb 2018
Doesn't this remove all rows between the two indicies?
Birdman on 1 Feb 2018
I changed it. Now check the answer.
Jason on 1 Feb 2018
Perfect, thanks Jason

Jos (10584) on 1 Feb 2018
I just want to point you to the following logic: if you start removing at the end, no indices will change:
A(ix2:end,:) = []
A(1:ix1,:) = []
However, you are much better off using Birdman's approach:
A = A(ix1+1:ix2-1,:) % include ix1 and ix2 for removal, per your example

1 Comment

Jason on 1 Feb 2018
Thankyou for this