Extract numbers from Matrix and create a matrix
1 view (last 30 days)
Show older comments
An M-by-M matrix X is given. Without using loops, extract values from matrix X to create the following:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/155582/image.jpeg)
%Generate an MxM matrix X. For part iv), X must have an even number of rows %and columns.
M = randi([20 40], 1);
M = M + mod(M,2);
X = magic(M);
===================================================
Maybe I just don't understand the problem.. how do I create a matrix for problem A, the dimension of matrix A is not given?
This is what I got for A, Is there a better answer than
A = a(:,1:2:end);
for problem A?
=====================================================
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/155585/image.jpeg)
Any body knows how to do B and C, I need some hints
0 Comments
Accepted Answer
Amit
on 25 Jan 2014
Edited: Amit
on 25 Jan 2014
For problem A, you are looking for odd rows and column, so the indexes should go for 1 with an increment of 2.
Like
A = X(1:2:end,1:2:end); % end simply represents the end
For B: you are excluding the first and last, so the indexes should exclude those.
B = X(2:end-1,2:end-1);
For C, I'd say first write down the indexes you're looking for on a piece of paper and see if you see a pattern. Post, even if it is wrong, and I'll tell you how to do it.
Sometimes it is easy to write out on a a piece of paper the indexes because it help you visualize.
3 Comments
More Answers (1)
Johnny
on 26 Jan 2014
Edited: Johnny
on 26 Jan 2014
1 Comment
Amit
on 26 Jan 2014
Your solution is a very good solution. I am glad you figured out diag. Other way would be: Lets say its a 5X5 matrix
C = [X(2:6:end)' X(6:6:end)'] % This method uses Linear indexing
Good luck in your studies and I hope you learn significantly about MATLAB Programming :)
See Also
Categories
Find more on Matrix Indexing 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!