Remove array values with multiple occurances from "parent" array

How do you remove values in an array from a "master database" array? For example:

a = [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4]

b = [1, 1, 2, 4, 4, 4]

I would like to remove each occurance of each value in 'b' from 'a' to get:

c = 1, 2, 2, 3, 3, 3

setdiff(a, b) doesn't work because it removes all instances from 'a' including the repeating values (it even says no repetitions in the documentation):

c = 3

[~, col] = ismember(b, a)

a(col) = []

doesn't work because it only removes one instance of the numbers (the first index where it occured):

c = 1, 1, 2, 2, 3, 3, 3, 4, 4

Thanks for the help.

Answer 1

[David Hill]

a = [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4];
b = [1, 1, 2, 4, 4, 4];
c = a;
for i=b
    c(find(c==i,1))=[];
end

[Joe I]

Awesome, thanks! Works great, scales up to my datasets with tens of thousands of values in each. Seems so obvious now after seeing it. Just be sure that each variable is a row vector.

Answer 2

[Bruno Luong]

Test samples

a = [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4]
b = [1, 1, 2, 4, 4, 4]

Code

u = unique([a,b]);
n = length(u);
[~, ia] = ismember(a,u); na = accumarray(ia(:),1,[n 1]);
[~, ib] = ismember(b,u); nb = accumarray(ib(:),1,[n 1]);
c = repelem(u,max(na-nb,0))

Result

c =

     1     2     2     3     3     3