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What is command for row echelon form of a matrix in MATLAB

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Ansha Nawaz
Ansha Nawaz 2017-10-21
评论： Nagabhushan SN 2019-9-19
A = 3 -1 0 4 1 2 0 3 3 -1 >> ref(A) ??? Undefined function or method 'ref' for input arguments of type 'double'.

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John D'Errico
John D'Errico 2017-10-21
Perhaps you are thinking of rref?
help rref
When you don't know the name of a function, learn to use lookfor. For example, when applied to the word "echelon", it returns this:
>> lookfor echelon
rref - Reduced row echelon form.
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Ansha Nawaz
Ansha Nawaz 2017-10-21
John D'Errico I have to apply Guass elimination,not Gauss-Jordan Elimination.
So, i just want echelon form not reduced echelon form

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Nagabhushan SN
Nagabhushan SN 2018-10-9
lu(A)
performs LU factorization of a matrix. So, you can get upper triangular matrix from there. Not sure though if it performs Gauss reduction
[L,U,P] = lu(A);
  2 个评论
Nathan Cleavinger
Nathan Cleavinger 2019-9-19
Thanks, Nagabhushan.
I had the same question, and that's exatly what I needed.
U = upper matrix (which is the ref - what we really want)
L = lower matrix, which is the coefficients used to eliminate elements
(i.e. to eliminate the first element on the second row, we'd used
(E2 - m21* E1) -> E2
and L stores all of the m__ coefficients. This is helpful when using other methods to solve matrices)
I'm not sure what P does.
Nagabhushan SN
Nagabhushan SN 2019-9-19
Hi Nathan, thanks for adding the details. Would help other people looking here.
And P is the permutation matrix. When you encounter a temporary breakdown when doing gauss elimination, you exchange the rows and proceed right, P captures that. In mathematical terms P*A = L*U

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