nunique

Calculate number of unique values of a variable as
  efficiently as possible.

internal

plyr is a set of tools that solves a common set of
        problems: you need to break a big problem down into manageable
        pieces, operate on each pieces and then put all the pieces back
        together.  For example, you might want to fit a model to each
        spatial location or time point in your study, summarise data by
        panels or collapse high-dimensional arrays to simpler summary
        statistics. The development of plyr has been generously
        supported by BD (Becton Dickinson).

nunique: Number of unique values.

Description

Usage

Arguments