plyr (version 1.6)

summarise: Summarise a data frame.

Description

Summarise works in an analagous way to transform, except instead of adding columns to an existing data frame, it creates a new one. This is particularly useful in conjunction with ddply as it makes it easy to perform group-wise summaries.

Usage

summarise(.data, ...)

Arguments

.data

the data frame to be summarised

...

further arguments of the form var = value

Examples

summarise(baseball,
duration = max(year) - min(year),
nteams = length(unique(team)))
ddply(baseball, "id", summarise,
duration = max(year) - min(year),
nteams = length(unique(team)))