How to remove a subset of elements from an ordered double array in Matlab-CodePudding

How do remove a subset of elements from a double array in Matlab? The arrays are ordered and 1-dimensional.

For example, given

A=[1,3,5,6,7];
a=[3,6];

desire

A_a=[1,5,7];

If a was scalar, I can do A_a=A(A~=a). How does it work if a is not scalar?

My concern with naïve looping around A_a=A(A~=a(i)) is that, seemingly, for every element a(i), a comparison is made for every element in A, which ignores the underlying order in the 2 arrays.

CodePudding user response：

Here are several ways to do this:

1. Using ismember to create logical indexing:

A_a = A(~ismember(A, a))

2. Treat A and a as sets, and use setdiff

A_a = setdiff(A, a)

3. Use arrayfun to generate logical indices

A_a = A(arrayfun(@(x)~any(x==a), A))

4. Good old fashioned for loop

A_a = []
for element = A
    if ~any(a == element )
        A_a(end 1) = element ;
    end
end