DESCRIPTION: This extension creates a new button on the VIEW toolbar which enables the user to calculate the weighted mean of a group of points. You have the option to create a RESULTS table containing this information, a new shapefile of the weighted mean center point, and/or a graphic symbol representing the weighted mean.
ALL OR ONLY SELECTED RECORDS: You can either use all the points in the point theme for the analysis, or only selected points. If any points in that theme are selected, then only those selected points in that theme will be used in the analysis. If no points in the theme are selected, then all points in that theme will be used in the analysis.
PROJECTED VS. UNPROJECTED VIEWS: If your original data are in Lat/Long coordinates (the Geographic Projection) and your View has been projected, then you have the option to calculating your mean center based on either the Geographic Projection or your View Projection. The choice of projections can dramatically affect the location of the mean of the point coordinates used in the analysis.
OUTPUT: Upon completion, you will have one or all of the following:
1) A Results table,
2) A Shapefile containing a single point representing the weighted mean center of the point theme, and/or
3) A Graphic Symbol displayed on the view representing the weighted mean center of the point theme.
REVISIONS: The 1.2b revision (Nov. 21, 2003) modifies the update script to avoid an “AVArray” error and modifies the calculation script to ignore null points. The 1.2c revision (March 11, 2004) modifies the calculation script to ignore null weight values, and produces a report notifying you if any null points or weight values were encountered.
An on-line version of the documentation may be viewed at:
http://www.jennessent.com/arcview/weighted_mean.htm
Please visit Jenness Enterprises ArcView Extensions site for more ArcView Extensions and other software by the author.
http://www.jennessent.com/arcview/arcview_extensions.htm
Enjoy! Please contact the author if you have problems with this extension.
Jeff Jenness |
