Command: linemerge

Syntax

linemerge <elist>

Description

Create one or more polyline graphic entities from the result of joining start/end vertices of other polyline and vector entities.

Parameters

• <elist>
  A group/entity list defining the entities to be merged. Only polyline and vector entities are considered.

Switches

• -ang=<angle>
  If the angle between possible candidates for connection is less than this angle, the polylines are assumed not to be connected. The default value is 0, which will resolve connections at any angle.

• -att=<attribute>
  A gstructure member providing a collating attribute. When this switch is present only polylines and vectors of the corresponding gstructure class are considered. Entities with identical values of "attribute" are grouped and new gstructure objects created from the resulting merge. All attributes from one of the original gstructure objects are transferred to the new gstructure objects. For example,

-att=~gis.roads_t.road_name

This will merge gstructure objects of class ~gis.roads_t which have the same value for road_name. The resulting new gstructure objects, also of type ~gis.roads_t, will have attributes transferred from one of the original gstructure objects, chosen at random. One distinct set of polylines (or one polyline depending on whether the -mul switch is present) is produced for every unique value of "attribute" within the source entities.

• -bls=<linestyle>
  A bridging linestyle. When new connections are made between polylines as a result of the -btol switch, this defines the linestyle of the joining line. If omitted, a null linestyle is assumed.

• -btol=<num>
  A bridging tolerance. When the extremities of 2 polylines are within this distance, the polylines are assumed to be connected and are joined by a bridging linestyle (see the -bls switch). Omitting this switch will mean no bridging is performed.

• -buf=<num>
  A buffering chunk size to improve performance. If this switch is included, polylines will be processed in chunks of num entities. This may mean that some connections get missed.

• -ef=<filter>
  A filter to be applied to all entities within elist, further qualifying which entities are to be merged. If omitted, the current filter is used.

• -g=<groups>
  The graphic groups into which the newly created entities are to be added.

• -mul
  By default, linemerge will create a polyline entity for every distinct polyline segment resulting from the merge. If this switch is present one polyline entity only is produced with "moves", i.e. null linestyles, between segments.

• -tol=<num>
  A closeness tolerance for edge and vertex matching. If omitted, a tolerance of zero is used.

• -wb=<points>
  2 points defining opposite corners of a clip rectangle. Only polylines and vectors which clash with this rectangle will be considered. Those which cross the rectangle will be clipped accordingly.

Notes

This command creates one or more graphic entities of type polyline.

All polylines created by a linemerge command form the contents of the group these.

Resulting polyline entities will have the same symbology as the original source entities.

The system numeric found records the number of polylines created by the linemerge command.

Examples

Merge all lines in a group (into "these").

linemerge ga

Merge all lines in a group collating on a gstructure attribute. One polyline gstructure is produced for each unique value of the attribute. Resulting entities are put into a group gb.

linemerge ga,-att=~gis.roads_t.road_name,-mul,-g=gb

See Also