  Monitoring data while it is processed and transformed can yield detailed
insight into the dynamics of a (running) production system. The lumberjack
package is a lightweight package allowing users to follow how an R object is
transformed as it is manipulated by R code. The package abstracts all logging
code from the user, who only needs to specify which objects are logged and what
information should be logged. A few default loggers are included with the
package but the package is extensible through user-defined logger objects.
