Variables in matrix not updating from for loop

21 views (last 30 days)
I am currently using a for loop in order to find the maximum eigenvalues of a matrix. The loop is as follows
for k = 0:c
e = eig(z)
M = max(e)
x = [x,M]
k = k+1
end
The variable k begins at 0, and the loop runs until c, a count of 50. z is the following 4x4 matrix: [k 0 2 0; 0 k 0 2; 3 4 5 0; 4 3 0 5]. What I am attempting to do is extract the maximum eigenvalue from the matrix, add it to an array x , then add 1 to k within the matrix, and continue until c is reached. However, k within the matrix is not updating, so it is simply finding the same eigenvalue 50 times. The k working the counter is performing as expected, but what do I have to do in order to make the k within the matrix update at each step as well?
  2 Comments
Scott MacKenzie
Scott MacKenzie on 22 Jun 2021
Edited: Scott MacKenzie on 22 Jun 2021
It would help if you provided all the code so it can be excuted to produce the error.
But, note that this line
k = k+1;
has no bearing on "k within the matrix".
Furthermore, k is the loop index variable in your for-loop, so it cannot be changed within the loop. So, there are a few issues to resolve.
Nolan Ames
Nolan Ames on 22 Jun 2021
That is all the code. If you're reffering to the variables, they are as follows. My assumption based on your response is I should likely change the loop index variable to something besides the matrix k to avoid future confusion.
c = 50
z = [k 0 2 0; 0 k 0 2; 3 4 5 0; 4 3 0 5]

Sign in to comment.

Accepted Answer

Scott MacKenzie
Scott MacKenzie on 22 Jun 2021
Edited: Scott MacKenzie on 22 Jun 2021
I think this is what you are looking for. It updates k in the z matrix in each iteration of the loop. The max values accumulate in the vector x.
c = 50;
k = 0;
z = [k 0 2 0; 0 k 0 2; 3 4 5 0; 4 3 0 5];
x = [];
for k = 0:c
e = eig(z);
M = max(e);
x = [x,M];
% update k in z
z(1,1)=k;
z(2,2)=k;
end
x % output max values
  1 Comment
Nolan Ames
Nolan Ames on 22 Jun 2021
That worked perfectly. Thank you for the timely response, I really appreciate it.

Sign in to comment.

More Answers (0)

Categories

Find more on Loops and Conditional Statements in Help Center and File Exchange

Products


Release

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!