# Running count in Table

To create a running count in an Excel Table, you can use the INDEX function with a structured reference to create an expanding range. In the example shown, the formula in F5 is:

When copied down the column, this formula will return a running count for each color in the Color column.

*In some versions of Excel, this is an array formula and must be entered with control + shift + enter.*

### How this formula works

At the core, this formula has uses INDEX to create an expanding reference like this:

INDEX([Color],1):[@Color] // expanding range

On the left side of the colon (:), the INDEX function returns a reference to the *first cell* in the column column.

INDEX([Color],1) // first cell in color

This works because, the INDEX function returns a *reference* to the first cell, not the actual value. On the *right* side of the colon, we get a reference to the *current row* of the color column like this:

[@Color] // current row of Color

This is the standard structured reference syntax for "this row". Joined with the colon, these two references create a range that expands as the formula is copied down the table. So, we swap these references into the SUM function, we have:

Each of the expressions above generates an array of TRUE/FALSE values, and the double negative (--) is used to convert these values to 1s and 0s. So, in the last row, we end up with:

SUM({0;0;0;1;0;0;0;0;1;0;1}) // returns 3

The rest of the formula simply concatenates the color from the current row to the count returned by SUM:

=[@Color]&" - "&3 ="Gold"&" - "&3 ="Gold - 3"

### Simple expanding range?

Why not use a simple expanding range like this?

SUM(--($B$5:B5=[@Color]))

For some reason, this kind of mixed reference becomes corrupted in an Excel Table as rows are added. Using INDEX with a structured reference solves the problem.

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