how to eliminate matrix?

ex [ 1 4 6 8 9; 5 7 9 5 3; 6 8 2 4 7; 4 3 2 1 0;] how can I do like this [ 1 4 6 8 9; 5 0 0 0 0; 6 0 2 4 7; 4 0 2 1 0;] or [ 0 0 0 0 0; 0 7 9 5 3; 0 8 2 4 7; 0 3 2 1 0;]

[Cedric]

I would recommend the official documentation:

http://www.mathworks.com/help/pdf_doc/allpdf.html

Under MATLAB, you could get..

• PDF labeled "MATLAB Primer" and study chapters 2 and 5.
• PDF labeled "Mathematics", and train to have a good mastery of chapters 1 and 9.
• PDF labeled "Programming Fundamentals" and have a look at the table of content so you can use it as a reference later.

The first two references will teach you how to index blocks of matrices. It's a good investment of your time to train a bit indexing. I am sure that after no more than 20-30 minutes spent on these references, you will know how to answer your question.

Answer 1

[Desiree Phillips]

This is a matter of matrix indexing techniques: see Matrix Indexing for details. If

A = [ 1 4 6 8 9; 5 7 9 5 3; 6 8 2 4 7; 4 3 2 1 0;]

Get [ 1 4 6 8 9; 5 0 0 0 0; 6 0 2 4 7; 4 0 2 1 0;] by using

A(2,2:end) = 0; % (Second row, Entries 2 to the end)

For [ 0 0 0 0 0; 0 7 9 5 3; 0 8 2 4 7; 0 3 2 1 0;] use

A(1,:) = 0; % Colon by itself means entire row

To eliminate the row, use [] instead of 0.