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

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Alon Rozen 2020년 2월 11일
댓글: Alon Rozen 2020년 2월 11일
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
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Stephen23 2020년 2월 11일
"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.

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### 채택된 답변

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);
##### 댓글 수: 6표시숨기기 이전 댓글 수: 5
Alon Rozen 2020년 2월 11일
Thanks Stepen!

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R2019a

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