# Basic syntax:
=SORT(A:A, COUNTIF(A:A, A:A), 0)
# Where:
# - this will sort column A by the number of occurrences of each item
# in column A
# - COUNTIF($A:A, $A:A) only counts the occurrences of A1 in column A.
# This is because COUNTIF is not an array formula. However, by
# wrapping it inside the SORT function, that makes it behave as an
# array formula, which causes it to return the count of each cell
# in column A in column A
# - SORT(A:A, ..., 0) sorts column A in descending order based on the
# counts
# Note:
# - if you want the unique occurrences of each item sorted by
# frequency, wrap the sort function with UNIQUE()
# - normally the second argument to SORT is the column number to sort
# by, but it seems like if you provide an array of numbers of the
# same length as the range, it uses those numbers first when
# sorting, followed by any additional columns you specify
# - the article this is based on uses IF(LEN(A:A), COUNTIF(...)). The
# IF(LEN(A:A),,) part prevents the formula from including blank
# cells, but isn't really necessary