# findgroups

Find groups and return group numbers

## Syntax

## Description

To split data into groups and apply a function to the groups, use the
`findgroups`

and `splitapply`

functions
together. For more information about calculations on groups of data, see Calculations on Groups of Data.

returns
`G`

= findgroups(`A`

)`G`

, a vector of group numbers created from the grouping
variable `A`

. The output argument `G`

contains
integer values from 1 to `N`

, indicating `N`

distinct groups for the `N`

unique values in
`A`

. For example, if `A`

is
`["b","a","a","b"]`

, then `findgroups`

returns `G`

as `[2 1 1 2]`

. In other words,
the group numbers in `G`

correspond to the sorted unique values
in `A`

.

To use `G`

to split groups of data out of other variables,
pass it as an input argument to the `splitapply`

function.

The `findgroups`

function treats empty character vectors and
`NaN`

, `NaT`

, and undefined categorical
values in `A`

as missing values and returns
`NaN`

as the corresponding elements of
`G`

.

creates group numbers from `G`

= findgroups(`A`

1,...,`A`

N)`A1,...,AN`

. The
`findgroups`

function defines groups as the unique
combinations of values across `A1,...,AN`

. For example, if
`A1`

is `["a","a","b","b"]`

and
`A2`

is `[0 1 0 0]`

, then
`findgroups(A1,A2)`

returns `G`

as
`[1 2 3 3]`

, because the combination ```
"b"
0
```

occurs twice.

`[`

also returns the sorted unique values for each group across
`G`

,`ID`

1,...,`ID`

N] = findgroups(`A`

1,...,`A`

N)`ID1,...,IDN`

. The values across
`ID1,...,IDN`

define the groups. For example, if
`A1`

is `["a","a","b","b"]`

and
`A2`

is `[0 1 0 0]`

, then
`findgroups(A1,A2)`

returns `G`

as
`[1 2 3 3]`

, and `ID1`

and
`ID2`

as `["a","a","b"]`

and ```
[0 1
0]
```

.

## Examples

## Input Arguments

## Output Arguments

## More About

## Extended Capabilities

## Version History

**Introduced in R2015b**

## See Also

`splitapply`

| `pivot`

| `unique`

| `ismember`

| `rowfun`

| `varfun`

| `arrayfun`

| `groupsummary`

| `discretize`

| `histcounts`

| `accumarray`

| `convertvars`

| `vartype`