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NAME

v.points.cog

DESCRIPTION

v.points.cog condenses points or centroids sharing a common attribute into a single point in a new vector map at their average position (center of gravity).

For this to work well your clusters of points must be gregarious (Gaussian distribution) - if two groups of points habitate in two corners of the map the output point will fall in the center and match niether well.

If needed you can use v.digit to adjust point positions created by this module, or use this module as a preprocessing step before running v.label.sa to deal with overlapping labels automatically.

EXAMPLE

Create single points at the average of all points in the bugsites map, and place a single label there. 
v.points.cog in=bugsites out=bug_cog column=str1

d.vect -c bugsites color=none icon=basic/circle

d.vect bug_cog disp=attr attrcol=str1 lcolor=black \
   lsize=14 xref=center yref=center bgcolor=white

SEE ALSO

v.label.sa
v.label
v.digit

AUTHOR

Hamish Bowman
Dept. Marine Science
University of Otago
Dunedin, New Zealand

Last changed: $Date$

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