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Calculate weighted centroids of zones   Albrecht Wirthmann Jan 27, 2010
Re: Calculate weighted centroids of zones   William Huber Jan 27, 2010
Re: Calculate weighted centroids of zones   Albrecht Wirthmann Jan 28, 2010
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Subject Calculate weighted centroids of zones 
Author Albrecht Wirthmann 
Date Jan 27, 2010 
Message I want to calculate weighted centroids of polygons but cannot find any function supporting this. I have a grid with population density and want to calculate centroids of regions (polygons) weighted by population count.
The result should be a list of region ids with the coordinates of the wieghted centroid of each region.

The method I am currently applying is to create a grid with column number, a grid with row numbers, multiply the populaton grid with the row and column grid. Do zonalstatistics as table and divide the sum of row*population grid by the sum of population grid by zone.

The generation of the row and column grid is very time consuming. Again, there is no command supporting this. I create a fishnet, add colums with row and column numbers an convert them into grid with pointgrid.

I am looking for a less time consuming solution to this problem, either directly computinh weighted centroids and facilitating the creation of a grid with row and column numbers for each grid cell.
 
   
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Subject Re: Calculate weighted centroids of zones 
Author William Huber 
Date Jan 27, 2010 
Message Use the Raster Calculator expressions $$YMap and $$XMap to generate the coordinate grids.

(BTW, there are other ways to obtain coordinate grids without going through a vector stage. For instance, they can be computed via FlowAccumulation from constant flow direction grids.) 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: Calculate weighted centroids of zones 
Author Albrecht Wirthmann 
Date Jan 28, 2010 
Message Thank you for the hint. It really saves time.

Albrecht