EXCEL: Copy cells from column A -> C ONLY IF column B = X, but only using 1 column

Question

I have 2 columns of data:

COL_A  COL_B
AAAA   PM
BBBB   PM
CCCC   P
DDDD   M
EEEE   PM

I want to create a 3rd column by filtering Column A

Answer 1

In C1 enter the array formula:

=IFERROR(INDEX($A$1:$B$20,SMALL(IF($B$1:$B$20="PM",ROW($B$1:$B$20)),ROW(1:1)),1),"")

and copy down:

Array formulas must be entered with Ctrl + Shift + Enter rather than just the Enter key.

You can increase the range in the formula to match your table size.

EDIT#1:

The INDEX() function pulls data from a column based on row. THE SMALL() function creates an array of rows matching the desired criteria.