[postgis-users] Create Voronoi Diagrams

[Greg Williamson]

%3% is looking for anything for a "3" in it -- similar to *3* so this would find 
every row for BOSTON with grades like .3, .03, 3.0, 1.3, 32, etc. that also have 
a type of "pub" ...

As to why the "WHERE" clause?

Perhaps this example is not trying to create a Voroni diagram for their entire 
database, but only for a relatively small number of rows.

Trying to create a Voroni diagram for a large data set will be slow and might 
exceed memory or other system resources, so unless your database is small, I'd 
try a subset of data, either limited by type or place name, or by a bounding 
box.

That said, I haven't used the referred function so I may be misleading with the 
best of intentions. :-}

HTH,

Greg Williamson






________________________________
From: ΑΠΟΣΤΟΛΟΣ ΛΕΛΕΝΤΖΗΣ <lelentzisapostolos at gmail.com>
To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
Sent: Tue, March 8, 2011 2:50:07 AM
Subject: [postgis-users] Create Voronoi Diagrams

Hello everybody

For another time, i ask your help and your experience!!
Specifically, i want to create voronoi diagrams with postgis, and i found the 
following intersting link
http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgresql_plr_tut02
So, i have installed the pl/r language and i have run the voronoi function.
But, i don't understand what kind of my data i have to place, at the below line 
code
WHERE town = ''BOSTON'' AND grades LIKE ''%3%'' AND type = ''PUB''
why the writer use a WHERE statement ?? 
what does mean the variable "%3%" ??

Thankss



      
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