How do I change certain value of a matrix by adding a something to the existing value?

I am very new to this.

I would like to change all the negative value of my matrix by 360+abs(existing value).

Let A be a matrix, I tried this:

A(A<0)=360+A

But it returns: Unable to perform assignment because the left and right sides have a different number of elements.

Could someone explain this to me?

Thank you

Answer 1

[David Hill]

A(A<0)=360+abs(A(A<0));

[A LL]

thank you!