Have you looked at this page in the documentation? http://mapserver.org/mapfile/expressions.html#arithmetic-operations-and-functions-that-return-a-number
You should be able to do this. You wouldn't use a CLASSITEM, just an expression. Create individual classes for green, yellow, and red. The expression for green would be something like: EXPRESSION ([PopulationOver65] / [PopulationTotal] * 100 < 10) David. -----Original Message----- From: mapserver-users-boun...@lists.osgeo.org [mailto:mapserver-users-boun...@lists.osgeo.org] On Behalf Of jjwang Sent: Thursday, September 08, 2011 12:47 AM To: mapserver-users@lists.osgeo.org Subject: [mapserver-users] how to define the CLASSITEM and EXPRESSION in this case? I want to define classes according to the proportion between two attributes of the feature. How to do this? For example: feature has two attributes 'PopulationOver65' and 'PopulationTotal'. They are both numbers. I want the color of this feature: green if PopulationOver65/PopulationTotal <10%, yellow if 10% -30%, red if 30%. Anyway to do this? JJ -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/how-to-define-the-CLASSITEM-and-EXPRESSION-in-this-case-tp6770598p6770598.html Sent from the Mapserver - User mailing list archive at Nabble.com. _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
