hello all.I have a big problem. i have a 5*3 matrix.I want to eliminate rows that the third column related to it, is less than 3.how can I do this? I have no idea. thanks a lot

for example:a=[1 2 3;4 3 2;1 4 6;8 3 0;2 4 1]; and the answer is: [1 2 3;1 4 6]

Answer 1

[Image Analyst]

Try this:

a=[1 2 3;4 3 2;1 4 6;8 3 0;2 4 1]; 
% and the answer is: [1 2 3;1 4 6]
% Find rows where the third column is less than 3.
rowsToDelete = a(:,3) < 3;
% Delete those rows.
a(rowsToDelete, :) = []

[fariba amini]

thanks a lot. it is really helpful.thanks again. can I ask one more question? let matrix 'a' contains 3 rows which the third column is less than 3, how can I choose 2 of these rows and then eliminate these two rows?

[Image Analyst]

Yes. Let's say that rowsToDelete had 3 rows in it, but that you wanted to delete only the first and last one, and the second one you wanted to keep (not delete). So just delete the second element from rowsToDelete:

rowsToDelete(2) = []; % Don't delete row in second location.

[fariba amini]

thanks a lot.