Get the column number of the false values in a logical output

I am trying to get the column numebr of the false values in a logical output called 'index'. My code is below

N = 50;
A = 1:N;
B = 1:41;

index = ismember(A,B);
C = index(index == 0);

Answer 1

[Rik]

You can use the find function:

N = 50;
A = 1:N;
B = 1:41;

index = ismember(A,B);
[row,col] = find(~index);
disp(col)

    42    43    44    45    46    47    48    49    50

[Vance Blake]

Thank you!