[Mapserver-users] Regular expression.

[Jean-Francois.Doyon at CCRS.NRCan.gc.ca]

If I rememebr correctly ( I could be wrong ), mapserver applies classes in
order, and a given feature can only belong to one class.

If I do rememebr this correctly, then you should be able to simple write out
your classes in the proper order in the mapfile with only one comparison and
get the same result:

[attr] < 2000
[attr] < 10000
[attr] < 20000

Here (hopefully) a feature would match a given class, and then processing
stops, giving you a "cumulative" effect.

The only potential problem with this way of doing it would be that you
couldn't have "gaps" below the top value (i.e. show ONLY 1000-1999 and
10000-19999).

If however my memory fails me right now and this is incorrect, I would
recommend you look at the spatial indexing tools (shptree*) that come with
MapServer, they can increase performance conciderably. Sorting the shapefile
with "sortshp" based on your attribute might also help?

J.F.

-----Original Message-----
From: krung [mailto:krung at cad.go.th]
Sent: Monday, February 24, 2003 12:25 PM
To: mapserver-users at lists.gis.umn.edu
Subject: [Mapserver-users] Regular expression.


Hi all,

I have a problem about using regexp. My dbf shapefile has one column with
number context. I would like to classify into range of number, e.g.

1000-1999, 10000-19999

How do I write this expression in map file?

CLASSITEM 'num_col'
CLASS
  EXPRESSION /.../  <- 1,000 to 1,999
  ......
END
CLASS
  EXPRESSION /.../ <- 10,000 to 19,999
  ....
END

I wouldn't like to use as:

  EXPRESSION ([num_col] >=1000 and [num_col] <=1999)
  ......
because it is very slow in rendering the image.

Thanks in advance.

Krung

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