MATLAB Answers

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

265 views (last 30 days)
A = 3 -1 0 4 1 2 0 3 3 -1 >> ref(A) ??? Undefined function or method 'ref' for input arguments of type 'double'.


Sign in to comment.

Accepted Answer

John D'Errico
John D'Errico on 21 Oct 2017
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.

  1 Comment

Ansha Nawaz
Ansha Nawaz on 21 Oct 2017
John D'Errico I have to apply Guass elimination,not Gauss-Jordan Elimination.
So, i just want echelon form not reduced echelon form

Sign in to comment.

More Answers (1)

Nagabhushan SN
Nagabhushan SN on 9 Oct 2018
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);


Nathan Cleavinger
Nathan Cleavinger on 19 Sep 2019
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 on 19 Sep 2019
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

Sign in to comment.

Sign in to answer this question.