# Power Pivot Principles: The A to Z of DAX Functions – COMBIN

10 May 2022

*In our long-established Power Pivot Principles articles, we continue our series on the A to Z of Data Analysis eXpression (DAX) functions. This week, we look at COMBIN.*

The COMBIN function

Are you often **COMBIN** the DAX functions to see how many subsets you can make? This function returns the number of combinations for a given number of items (*i.e.* the number of distinct subsets of items where order is unimportant). You should use **COMBIN** to determine the total possible number of groups for a given number of items.

The **COMBIN **function employs the following syntax to operate:

**COMBIN(number, number_chosen)**

The **COMBIN** function has the following arguments:

**number:**this is required and represents the number of items**number_chosen:**this is also required. This denotes the number of items in each combination.

It should be further noted that:

- numeric arguments are truncated to integers
- if either argument is nonnumeric,
**COMBIN**returns the*#VALUE!*error value - if
**number**< 0,**number_chosen**< 0, or**number**<**number_chosen**,**COMBIN**returns the*#NUM!*error value - a combination is any set or subset of items, regardless of their internal order. Combinations are distinct from permutations, for which the internal order is significant
- the number of combinations is as follows, where
**number**=**n**and**number_chosen**=**k**:

where:

- and
**n!**denotes**n**x (**n**– 1) x … x 2 x 1 - this function is not supported for use in DirectQuery mode when used in calculated columns or row-level security (RLS) rules.

Please see my example below:

Sorry to ruin the ending of Series 927 for you…