This is an example of extracting time/date information from a mail log, generating a histogram of how many mail messages were received per hour, and generating some simple statistics.

The output looks like this:

Uses inline code and the histProcs.tcl library to generate the display.
Uses procedures from the Tcllib math::statistics library to perform the simple statistics operations.
A set of procedures for doing scaling, drawing the X and Y axis and defining reasonable step sizes for each axis.
The sample mail log file, truncated to date and system name.