MS Excel: Count the number of cells in a column that have the same number as the cell to the left of it

Question

How can I do to count the number of cells in a column, that have the same text as the cell to the left of it?

Seems it should be pretty simple but I can't find a way or any answer online. Thank you.

=COUNTIF(P$2:P$125,"="&$O2)

=COUNTIF(P$2:P$125,"="&$O2)

This is almost perfect except the formula tries to match always with cell value of O2. Which is great for P2, but when I get to P99 for example, I want to see if it is exactly the same as O99, and similarly then equal.

Answer 1

Use SUMPRODUCT and limit the ranges to the extents of the data while maintaining the same size of range for both columns.

=SUMPRODUCT(--(O$2:O$125=P$2:P$125))
'dynamic range
=SUMPRODUCT(--(O$2:index(O:O, match("zzz", O:O))=P$2:index(P:P, match("zzz", O:O))))

The -- (or double unary ) coverts the TRUE/FALSE results to ones and zeroes.