How to operate on 2d matrices in a 3D array?

24 views (last 30 days)
Hi,
I have a set of n 3x3 matricies orgenized in a 3D array with dimesions 3x3xn.
I want to operate on all 3x3 matricies: I want to get a vector of determinants and a vector of trace of each 3x3 matrix.
I also want to calculate a 3x3xn array which will hold the 3x3 inverse of each matix.
I can do it using a for loop, of couse, calculating in each iteration for the ith matrix.
Is there a simpler and faster way to do it?
Thanks,
Alon
  1 Comment
Stephen23
Stephen23 on 11 Feb 2020
Edited: Stephen23 on 11 Feb 2020
"Is there a simpler and faster way to do it?"
Calculating the matrix inverse is rarely required or nor efficient when doing numeric computing. Read this to know why:
If you are really interested in efficiency, then use better tools than inv, just as the documentation recommends.
The determinant also tends to be overused by beginners who do not realize how useless it is in numeric computing. Search this forum to know why the determinant is essentially useless in numeric computing.

Sign in to comment.

Accepted Answer

Bhaskar R
Bhaskar R on 11 Feb 2020
data = randi([1,10], 3,3,4); % your matrix with n = 4
data_det = arrayfun(@(i)det(data(:,:,i)), 1:size(data,3));
data_trace = arrayfun(@(i)trace(data(:,:,i)), 1:size(data,3));
data_inv = arrayfun(@(i)inv(data(:,:,i)), 1:size(data,3), 'UniformOutput', false);
  6 Comments
Stephen23
Stephen23 on 11 Feb 2020
"Why is that?"
Essentially because repeatedly calling a function handle that runs sme code is slower than just calling that code directly.
"If I will use only one fuction that returns all calculation results, it also will be slower then a loop?"
Probably... try it and find out.

Sign in to comment.

More Answers (0)

Categories

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

Products


Release

R2019a

Community Treasure Hunt

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

Start Hunting!