[Mapserver-users] classifications on the fly

[Sean Gillies]

On Feb 18, 2004, at 11:35 AM, Bart van den Eijnden wrote:

> Hi list,
>
> can Mapserver do classifications on the fly, e.g. equal range, equal 
> count, unique value etc.? If not, does anybody know of another open 
> source tool/product to do this, or perhaps there are plans to support 
> it in Mapserver/Mapscript? This would allow a user to classify data as 
> they see fit.
>
> The result of a classification "request" could be an SLD document 
> (which after optionally being changed by a user with regard to 
> symbology, could be used in combination with a GetMap request to see 
> the result of the classification). But I can't seem to find a 
> specification for "classification services" in the OGC world, anybody 
> know of any relevant specification?
>
> Thanks in advance.
>
> Best regards,
> Bart

Bart,

You'll have to roll your own classifier, but mapscript will allow it.  
I'm doing it
for my ZMapServer project (code not yet in CVS).  It's not too 
difficult.  Open
a layer, query it to get records, iterate over the query to get unique 
values of
an attribute (or item as mapserver calls it).  Then create new classes 
in a layer
for each unique value.

Putting a classifier into mapserver itself could really slow it down, 
particularly
if you are classifying on unique values.

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies