Filters

Crash Magic has a powerful feature called the filter.  The filter enables the user to perform ad-hoc queries of the database or any current report.  It can be used to gather crashes for a diagram, high crash location list, chart, etc.  It can also be used to limit those crashes shown in a diagram after it has been generated.

Because the filter is tied to the study, all reports based on a particular study are therefore linked to that filter.

The filter is a true/false statement.  Any time an crash is going to be evaluated, it is first checked against the current filter.  If each statement in the filter is true for the given record, then the record is included, otherwise that record is excluded from the current report or diagram.  Common uses for the filter is to impose a "distance cutoff" beyond which crashes are said to have "not been intersection related".

The filter can be modified by selecting filter button at the bottom of any study or report.  The resulting dialog box will have space to enter a filter.

Distance < 100

This would exclude all crashes where distance was greater than or equal to 100.  The next example builds on this:

(( Distance > 0 ) .AND. ( Distance < 200 )) .AND. (Type_Of_Coll = Type_Of_Coll.Rear_End)

This can be read as: Include only crashes where Distance was between 0 and 200, and Type of Collision was Rear end.