summarise {plyr} | R Documentation |
Create a new data frame that summarises an existing data frame.
summarise(.data, ...)
.data |
The data frame to be summarised |
... |
Further arguments of the form var = value |
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.
Hadley Wickham <h.wickham@gmail.com>
summarise(baseball, duration = max(year) - min(year), nteams = length(unique(team))) ddply(baseball, "id", summarise, duration = max(year) - min(year), nteams = length(unique(team)))