matrix unions

if array A = 10 x 1 with numbers in it and array B = 4 x 1 with numbers in it. How would you create an array C which equals the size of A and is filled with NaN except for the points where A and B equal the same value.

A = [ 1 2 3 4 5 6 7 8 9 10]

B = [ 1 3 5 7]

I would like:

C = [1 NaN 3 NaN 5 NaN 7 NaN NaN NaN]

thanks for the help

Answer 1

[Geoff]

You can use a real handy function called ismember() to test elements of A against elements of B. Then it's just a matter of indexing:

in = ismember(A,B);
C = nan(size(A));
C(in) = A(in);

Answer 2

[Andrei Bobrov]

C = A
C(~ismember(A,B)) = nan

OR

C = A
C(setdiff(A,B)) = nan