Wrong answers given by MATLAB LU Factorization
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LU factorization or decomposition method is supposed to decompose a square matrix to a lower matrix and a upper matrix. However, I tried to test some 2 by 2 matrix, the MATLAB LU method sometimes give me 2 upper matrix. Such an original matrix as:
A=[4 , 3 ; 6 , 3]
The answer given by MATLAB:
[L,U]=lu(A)
L=[0.667,1 ; 1, 0]
U=[6, 3 ; 0, 1]
The correct answer should be
L=[1 , 0 ; 1.5, 1]
U=[4 , 3 ; 0, -1.5]
I don't understand why MATLAB gives me such answer
Please, someone help me!
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Answers (2)
Sean de Wolski
on 15 Jan 2014
The behavior you are seeing is described in Example 1 of the lu documentation:
José-Luis
on 15 Jan 2014
Both answers are valid.
A = [2/3,1 ; 1, 0] *[6, 3 ; 0, 1]
B = [1 , 0 ; 1.5, 1] * [4 , 3 ; 0, -1.5]
A == B
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