get common position in cell array and replace with specific values

idx = [ 3  6  7 ] ;
ids = [ 2  3  5  6  7 ] ;

i have a cell of size 1 x 8

Initially all values in cell_array of size 1 x 8 is 'AB'

i want, the value in cell_array positions [3 6 7] (which is common in both idx and ids) to be wriiten as 'A' and the other values not in idx as 'B'

and those positions not in idx or ids, leave as it is (in our case 'AB')

[madhan ravi]

What about 7?

Answer 1

[Jan]

C     = repmat({'AB'}, 1, 8);
idx   = [ 3  6  7 ] ;
ids   = [ 2  3  5  6  7 ] ;

index    = intersect(ids, idx);
C(index) = {'A'};
index    = setdiff(ids, idx);
C(index) = {'B'};

Or leaner:

m          = ismember(ids, idx);
C(ids(m))  = {'A'};
C(ids(~m)) = {'B'};

Or:

Pool   = {'B', 'A'};
C(ids) = Pool(ismember(ids, idx) + 1)