updated: 21-Sep-2010

 Copan for Windows

Point Filters

Contents
  1. To Filter Points
  2. Filter Criteria
  1. Text Expressions
  2. Notes

At times you may wish to view or work with a specific subset of points from an open coordfile, rather than the whole file. You can establish such a subset by specifying a filter (or query). Typically, to specify a filter, you just identify sequences or ranges of point numbers. You can, however, also identify ranges of coordinate values, as well as conditions for the three alphanumeric fields.

1. To Filter Points

Click on Filter within various dialogs or choose it from the Viewing menu.

  1. Click the Filter... button from whichever module is processing a group of points
    or choose Viewing & Printing | Filter Points... to restrict the viewing of points.
  2. Optionally, select an existing filter from the Filter list box.
  3. Enter or edit the details of the filter (see Filter Criteria below).
  4. Optionally, enter a new name for the filter in the Filter list box.
  5. Click OK.

Enter ranges of point numbers, choose other criteria, and click OK.

2. Filter Criteria

3. Text Expressions

Syntax

In these quasi-formal syntax definitions, a defined term (outdented) is followed by its definition (indented), with alternative definitions separated by vertical lines or on separate lines. Puzzled? See the Examples.

text-expression
predicate
text-expression   logical-operator   text-expression
( text-expression )
predicate
relational-operator   value
relational-operator
= | ? | != | <> | < | > | <= | >=
value
any text | " any text containing a special character "
logical-operator
& | ,

Relational and Logical Operators

Operator Meaning
= equal to
? containing
!= or <> not equal to
< alphabetically before
> alphabetically after
<= alphabetically before or equal to
>= alphabetically after or equal to
& logical and
, logical or
( ) logical group, required when logical or must be evaluated before logical and

Examples

Expression Meaning
="" is null (blank)
<> "" is not null (not blank)
= 13, =14 equal to 13 or 14
<> 12 & <> 16 equal to anything but 12 or 16
? O & ? P containing O and P
>= G & < K beginning with letters g to j
? BC & (? "?", ? "!") containing BC and containing ? or !

4. Notes