dataEdit-class: Reference Class for Editing Data Table Objects
In johnmchambers/XRexamples: Extending R: Examples

A subclass of dataTable-class objects, in which elements in a column can be edited by supplying new values for a range of rows, and the edits can be undone.

edits: A list that keeps account of the edits performed.
description: A character string with a description of the edit project.

edit(i, var, value): Replaces the range i in the variable named var in the object by value.
initialize(..., data = data.frame()): This method takes data= as a named argument, but coerces it to be an environment, instead of requiring that it already be one.
undo(): Undoes the last edit() operation and updates the edits field accordingly.