# Distributions of tips consistent with a partition pair

Source:`R/SplitFunctions.R`

`NPartitionPairs.Rd`

`NPartitionPairs()`

calculates the number of terminal arrangements matching
a specified configuration of two splits.

## Details

Consider splits that divide eight terminals, labelled A to H.

Bipartition 1: | ABCD:EFGH | A1 = ABCD | B1 = EFGH |

Bipartition 2: | ABE:CDFGH | A2 = ABE | B2 = CDFGH |

This can be represented by an association matrix:

A2 | B2 | |

A1 | AB | C |

B1 | E | FGH |

The cells in this matrix contain 2, 1, 1 and 3 terminals respectively; this
four-element vector (`c(2, 1, 1, 3)`

) is the `configuration`

implied by
this pair of bipartition splits.

## Examples

```
NPartitionPairs(c(2, 1, 1, 3))
#> [1] 12
```