How to get an array "complement" of another?

Question

the easiest way for me to explain what i want is with an example:

a = 1:20

b = [2,7,12,18]

Now I want c to be [1,3,4,5,6,8,...,19,20] with length 16: length(a) - length(b) of course.

Is there a way for me to get c?

Answer 1

What you want is called set difference in most languages. In MATLAB, you can use the setdiff function:

a=1:20;
>> b=[2,7,12,18];
>> setdiff(a,b);

ans =

Columns 1 through 11

 1     3     4     5     6     8     9    10    11    13    14

Columns 12 through 16

15    16    17    19    20