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

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

Answer 1

[John D'Errico]

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.

[Ansha Nawaz]

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

Answer 2

[Nagabhushan SN]

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);

[Nathan Cleavinger]

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]

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