单个单词的平均计数的单单元格计算

Question

I have a dataset that looks as follows:

Apple
Banana
Banana
Carrot
Pear
Pear
Pear
Pear
Pear

I'd like to use a formula to find out on average how many times an item appears in the list. At the moment, I create another table listing each item just once and then use COUNTIF to find the number of times each item appears:

Apple  1
Banana 2
Carrot 1
Pear   5

In another cell, I then average these numbers to reach a figure of 2.25.

Is there a way to simplify this and calculate it using an (array?) formula in a single cell?

Thanks in advance!

Answer 1

You do not require an array formula:

=COUNTA(A1:A9)/SUMPRODUCT(1/COUNTIF(A1:A9, A1:A9))

EDIT#1:

It turns out that the average of the unique counts is actually:

=(total count of items) / (count of uniques)

EDIT#2:

To cover the entire column and exclude blanks, use the Array Formula :

=COUNTA(A:A)/SUM(IF(A:A<>"",1/COUNTIF(A:A,A:A ), 0))

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

This is painfully slow to calculate, so I recommend restricting the cells in column A to something reasonable.