Construct an immutable data frame.

Description

An immutable data frame works like an ordinary data frame, except that when you subset it, it returns a reference to the original data frame, not a a copy. This makes subsetting substantially faster and has a big impact when you are working with large datasets with many groups.

Usage

idata.frame(df)

Arguments

Details

This method is still a little experimental, so please let me know if you run into any problems.

Value

an immutable data frame

Examples

system.time(dlply(baseball, "id", nrow))
system.time(dlply(idata.frame(baseball), "id", nrow))