Property Filter

The Property Filter is the most general type of filter. Using this filter type you could in theory do the job of all the other filter types. But the drawbacks of this filter type are that it is more complicated to use, and will probably operate slower than the other specialised filters.

The Property Filter is a mathematical expression, which you can edit as simple text. The expression can use item properties as well as numbers. See Property Expression Syntax for more details.

To see whether an item passes the filter, the expression is evaluated. If the expression evaluates to a non-zero value then the item is included.

Here are some examples of expressions:

_FC&=1 _FC&<>98 (_FC&=1) or (_FC&=1006) or (_FC&=98) (_FC&=1) and _closed& _class$="Line" _np&>78 len(_text$)>6 grep("[0123456789]",_text$)
The reason that Property Filter objects operate slowly is that the software must evaluate the expression, and interrogate the item for each property that the expression uses.

Some item properties may appear esoteric, like Thin in X and Thin in Y, but they can be useful (for instance to find horizontal and vertical lines as part of a data cleaning exercise).

Send comments on this topic.

Click to return to www.cadcorp.com