Symbolizing polygons

[Stephan Dunning]

>Doug wrote:
>I wish to serve a map which, for example sake, will illustrate
>several classes of polygon as red, yellow, and green (for example
>sake) creating a choropleth map based on an attribute in the 
>associated table. 
>
>Can someone point me to a nice example where this is done so I
>can see what the map file would look like? I believe I will need
>to regenerate the map file when the attributes change, yes?

"Nice" may be a strong word :), but here's an example of something I had
originally put together:
http://mapserver.geog.umn.edu/cgi-bin/mapserv?map=/home/stephan/public_html/
hsa.map&layer=prevrate

Here too is a sample from my original mapfile with the first of 18 layers.  
The layer names the Classitem, then uses the Expression line to associate a
classitem value with a RGB color.
The the Class "Name" populates the legend labels.
MAP
  NAME "hsa"
  EXTENT -1700000 3000000 3100000 5500000
  SIZE 550 400
  SHAPEPATH "data"
  UNITS meters
  IMAGECOLOR 230 220 190

  WEB
    IMAGEPATH "/pkg/mapserver_web_root/htdocs/tmp/"
    IMAGEURL "/tmp/"
    TEMPLATE hsa.html
  END

  SCALEBAR
    STATUS ON
    IMAGECOLOR 230 220 190 
    INTERVALS 4
    SIZE 200 2
    COLOR 0 0 0
    OUTLINECOLOR 0 0 0
    BACKGROUNDCOLOR  255 255 255
    UNITS kilometers
    LABEL
      COLOR 0 0 0
      SIZE small
    END
  END

  QUERYMAP
    STATUS ON
    SIZE 300 200
    STYLE HILITE
  END

  REFERENCE
    STATUS ON
    IMAGE graphics/hsa1.gif
    SIZE 250 151
    EXTENT  -1700000 2700000 3100000 5800000
    COLOR -1 -1 -1
    OUTLINECOLOR 0 0 200
  END
 
  LEGEND
    STATUS ON
    IMAGECOLOR 230 220 190
    LABEL
      COLOR 0 0 0
    END
  END

  LAYER
    NAME prevrate
    DATA hsaprev2
    STATUS OFF
    TYPE POLYGON
    DESCRIPTION "1998 Prevalent Population (As a % of Total Population)"
    CLASSITEM "Qprev"
     CLASS
      EXPRESSION "5"
       OUTLINECOLOR 0 0 0
       COLOR 0 0 185
       NAME "0.1222 +"
     END
     CLASS  
      EXPRESSION "4"
       OUTLINECOLOR 0 0 0
       COLOR 41 41 255
       NAME "0.101-0.1222"
     END
     CLASS
      EXPRESSION "3"
       OUTLINECOLOR 0 0 0
       COLOR 99 99 255
       NAME "0.0872-0.101"
     END
     CLASS 
      EXPRESSION "2"
       OUTLINECOLOR 0 0 0  
       COLOR 175 175 255
       NAME "0.0718-0.0872"
     END
     CLASS
      EXPRESSION "1"
       OUTLINECOLOR 0 0 0
       COLOR 225 225 255
       NAME "below 0.0718"
     END
     CLASS
      EXPRESSION "0" 
       OUTLINECOLOR 0 0 0
       COLOR 255 255 255
       NAME "Insuff. Data"
     END
     QUERY
       TEMPLATE "hsainfo.html"
     END
  END
END


Hope this helps!
Stephan


-----Original Message-----
From: Doug Nebert [mailto:ddnebert at fgdc.gov]
Sent: Tuesday, December 19, 2000 12:45 PM
To: Mapserver Users
Subject: Symbolizing polygons


I wish to serve a map which, for example sake, will illustrate
several classes of polygon as red, yellow, and green (for example
sake) creating a choropleth map based on an attribute in the 
associated table. 

Can someone point me to a nice example where this is done so I
can see what the map file would look like? I believe I will need
to regenerate the map file when the attributes change, yes?

Doug.
-- 
Douglas D. Nebert
Geospatial Data Clearinghouse Coordinator 
FGDC/GSDI Secretariat	Phone: +1 703 648 4151	Fax: +1 703 648-5755	
Pager Messaging: 	http://clearinghouse3.fgdc.gov/dougmsg.html