How to replace values of certain rows in a matrix?
20 views (last 30 days)
Show older comments
Hi,
I have a matrix "a"
a =
1 1
2 2
3 3
4 4
I would like to replace the 2nd and 3rd row in "a" with "b" = [0 0]. So I want to change "a" to
a =
1 1
0 0
0 0
4 4
Do I have to do it in a loop? Can I avoid the loop?
0 Comments
Answers (1)
Adam
on 18 Oct 2019
Edited: Adam
on 18 Oct 2019
a( [2 3], : ) = repmat( b, 2, 1 )
A bit more generally:
indicesToReplace = [2 3];
a( [2 3], : ) = repmat( b, indicesToReplace, 1 );
1 Comment
dpb
on 18 Oct 2019
Edited: dpb
on 18 Oct 2019
For the OP's specific case of replacing with a constant, automagic expansion negates need for repmat.
a(indicesToReplace,:)=0;
Side note to OP--work through the example tutorials in the "Getting Started" documentation link to get a feel for basic MATLAB syntax and addressing modes including colon and friends...will be an investment in time paid back many times over.
See Also
Categories
Find more on Logical in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!