Checking of equality for two matrices

Hi I have trouble coming out the code to find the equality of two matrices. I have to test and display that the matrices are equal. I am trying to include 'if' statement in as well.

Here is the question:

Calculate AxB and BxA and test if AB = BA.

Thanks!

[Martin C.]

isequal(A,B) should do it

cheers

[Ian Thean]

I am torn between result = A==B and isequal(A,B).

I believe it would help me partly in this coding. Thanks!

[Guillaume]

Have you actually tested the difference between the two? It should be very obvious.

A == B will return a matrix the same size as A (and B) telling you which elements of A are equal to the corresponding element of B.

isequal(A, B) will return a single true/false telling you if all the elements of A are the same as the ones in B.

[the cyclist]

An advantage of using isequal(A,B) over A==B is that if A and B are different sizes (e.g. 4x4 vs. 3x3), then A==B will throw an error because of the dimension mismatch, but isequal will return a result.

This may not be important in your specific case, but could be in general.

[the cyclist]

Also, I think you mean to check isequal(A*B,B*A), not just isequal(A,B).

Be aware of the accuracy of floating-point numbers for exact equality check.

Answer 1

[Rik]

The difference between the isequal function and the == operator is that the second will work element by element. That means that isequal will tell you if two matrices are the exact same, while == will test all elements individually.

One golden tip: always make sure your input to if or while is a scalar, not a logical array. Array input tend to do something different from what you might mean.