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will99
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How can I generate reciprocal of a matrix

Asked by will99
on 19 Apr 2019
Latest activity Answered by Star Strider
on 19 Apr 2019
I have big matrix A 500 by 500 and I want to generate reciprocal of matrix A
what caluclation shuould I do or is there a function in matlab that I can use
%Matrix A
A = [2, 3, -1, 5; -1, 4, -7, -3; -6, 0, 3, 9; 7, 6, -3, 8];
%Matrix X, reciprocal of matrix A
X= ....

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2 Answers

Answer by Star Strider
on 19 Apr 2019
 Accepted Answer

It depends on what you mean by ‘reciprocal’. If you want ‘X’ such that:
A*X = eye(size(A,1))
then:
X1 = inv(A); % Inverse
X2 = pinv(A); % Pseudo-Inverse
will do what you want.
There are many precautions about calculating the inverse that you will likely encounter. A much better option would be to use the mldivide,\ (link) function if you want to solve linear systems, for example.

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Answer by Walter Roberson
on 19 Apr 2019

I suspect that you want inv(A) but possibly you want 1./A
In most cases inv() is better avoided in favor of using the \ operator or decomposition

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