plyr (version 1.4.1)

summarise: Summarise a data frame.

Description

Summarise a data frame. Create a new data frame that summarises an existing data frame.

Usage

summarise(.data, ...)

Arguments

.data

the data frame to be summarised

...

further arguments of the form var = value

Details

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.

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)))