CONNECTIVITY

Calculates various statistics to measures the connectivity of a set of polygons.  To connect the polygons, a line is drawn from the centroid of one polygon to the next until all of the polygons are connected.  The results are stored in global variables.

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CONNECTIVITY <in_cover> {out_cover} [selection_file} {dispersal_distance} {total_passes}

ARGUMENTS

<in_cover> - the input polygon coverage.

{out_cover} - the name for the output line coverage.

If not specified, the line coverage is not saved.

{selection_file} - the name of a selection file that identifies which polygons to analyse.

If not specified, all polygons are used.

{dispersal_distance} - used in calculation of .cnt$index3.

If not specified, 0 is used.

{total_passes} - total number of passes made through the network of polygons.

No two polygons can be connected to each other more than once.

If not specified, 1 pass is made.

OUTPUT

The results are stored in four global variables:

.cnt$index1 - the mean connection length between polygons relative to a theoretical maximum.  The value ranges from 0 (very low connectivity) to 100 (very high connectivity).

.cnt$index2 - Same as index1, but uses root mean squared.

.cnt$index3 - the percentage of connections less than or equal to the {dispersal_value}.

.cnt$index4 - the percentage of the length of the connection line that falls within polygons.

NOTES

- This AML assumes the polygons are roughly the same size.