A B
china P1
korea P2
japan P3
china P2
korea P2
japan P1
U.S P2
India P1
China P1
U.S P2

I'm working with about 8000 data, I try to used this formula
=SUM(IF(FREQUENCY(MATCH(A1:A10,A1:A10,0),MATCH(A1:A10,A1:A10,0))>0,1)) to
count the unique entries in column A, which result 5. (China,
japan,korea,india,U.S)

However, i want to count unique entries in, let say P1 only, which should be
3. How to use function to get this result?