Just wondering if anybody has played around with the proportional sum
functions.
In the MB manual under the Add Column statement it says to use "where
within" at the end of the command. i.e.
add column Road_Offset(dwellings) from Stats_data set to proportion
sum(No_of_dwellings) where within
After researching what "where within" actually means I find that its
based on centroids. So if some of my base polygons centroids are not
within my road offset polygon. Can I assume that the data from these
will not be included? I changed my code to:
add column Road_Offset(dwellings) from Stats_data set to proportion
sum(No_of_dwellings) where intersects
and got a completely different answer? Would the intersects option be
more appropriate  when the base data must intersect at some point, but
the centroids will not necessarily fall within the polygon? Is this just
a typo in the manual?
Cheers
Tony
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Tony Shepherd, GIS / IT Support
Gore District Council
PO Box 8, Gore, New Zealand
Gore, The Brown Trout Capital

.. .. .. .. coming soon! .. .. .. ..
.. . www.mataura.com . ..
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