Problem with if and than and det

Question

bondpen 2018-4-12

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https://ww2.mathworks.cn/matlabcentral/answers/394358-problem-with-if-and-than-and-det

关闭： bondpen 2018-4-13

So basically im trying script that determines if matrix is singular or not, by doing a det on the matrix. For example i tired doing: det([1 2;3 4]) which result in zero, but when I tired to input into the command like singularitytest([1 2;3 4]) or A=[1 2;3 4] its output is just the matrix. I am not sure which part i have gotten wrong, the If and else statements or the det? or my input command?

function result = singularitytest(A)
         if det(A) == 0
            c = 0;
         else
            c = 100;
end

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Stephen23 2018-4-12

编辑：Stephen23 2018-4-12

Note that using the determinant is not a good way to check if a numeric matrix is singular. It works in abstract mathematics, but not for real-life numeric matrices. This has been discussed many times on this forum:

https://www.mathworks.com/matlabcentral/answers/389977-does-the-function-chol-correctly-indicates-that-a-matrix-is-positive-definite

https://www.mathworks.com/matlabcentral/answers/381548-using-matlab-s-det-why-does-this-3x3-matrix-s-determinant-not-zero

https://www.mathworks.com/matlabcentral/answers/131506-is-the-rank-function-reliable

etc. etc.

bondpen 2018-4-13