[postgis-users] Creating a Flow Diagram

[Bob Pawley]

Andy

I've been trying the changes you suggested without success.

I get an error when I use the + operator (and also if I leave out temp_).

Perhaps I don't understand the use of st_y, st_x max and min.

I don't want to change the entity merley move it from where it is to the 
center of an established geometry (box).

Here's the function as it now stands. I still get 0 rows affected and the 
two tables do have geometries (one entity in process_dgm and one box in 
spatial_ref where position = 2) in them.

 Insert into temp_ (the_geom)
 Select st_translate (st_translate(graphics.process_dgm.the_geom,
 st_x (st_centroid(graphics.process_dgm.the_geom)) - st_x (st_centroid 
(spatial_ref.the_geom)),
 st_y (st_centroid(graphics.process_dgm.the_geom)) - st_y (st_centroid 
(spatial_ref.the_geom))),
 ( st_xmax(graphics.process_dgm.the_geom) - 
st_xmin(graphics.process_dgm.the_geom)),
 ( st_ymax(graphics.process_dgm.the_geom) - 
st_ymin(graphics.process_dgm.the_geom)))

 from graphics.process_dgm, spatial_ref, temp_
 where graphics.process_dgm.description = 'Tank'
 and spatial_ref.position_ = 2 ;

Bob


----- Original Message ----- 
From: "Andy Anderson" <aanderson at amherst.edu>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Sunday, June 08, 2008 7:25 PM
Subject: Re: [postgis-users] Creating a Flow Diagram


> On Jun 8, 2008, at 5:14 PM, Bob Pawley wrote:
>> I 'm playing with a variation of the st_translate function we were 
>> discussing last week.
>>
>> I have created two boxes (spatial_ref) and I wish to place an entity 
>> (graphics.process_dgm) into the temp_ table with the coordinates  that 
>> centers the entity in a specific one of these boxes.
>>
>> Here's the code that I have come up with but so far it produces 0  rows.
>>
>> Insert into temp_ (the_geom)
>
>> Select st_translate(st_translate (graphics.process_dgm.the_geom,
>> st_y (st_centroid(graphics.process_dgm.the_geom)) - st_x  (st_centroid 
>> (spatial_ref.the_geom)),
>
> The first function here should be "st_x", not "st_y".
>
>> st_y (st_centroid(graphics.process_dgm.the_geom)) - st_y  (st_centroid 
>> (spatial_ref.the_geom))),
>> ( st_xmax(graphics.process_dgm.the_geom) - 
>> st_xmin(graphics.process_dgm.the_geom)),
>> ( st_ymax(graphics.process_dgm.the_geom) - 
>> st_ymin(graphics.process_dgm.the_geom)))
>
> I don't see anything wrong with this, but you should be able to make a 
> single st_translate call here since max - min won't change in a 
> translation, e.g.
>
> (st_y (st_centroid(graphics.process_dgm.the_geom)) - st_x (st_centroid 
> (spatial_ref.the_geom))) + ( st_xmax(graphics.process_dgm.the_geom) - 
> st_xmin(graphics.process_dgm.the_geom))
>
> So after matching the centroids you're trying to move the lower left 
> corner of the bounding box to its upper right corner?
>
>> from graphics.process_dgm, spatial_ref, temp_
>
> I don't think you need the ", temp_", but it probably doesn't hurt.
>
>> where graphics.process_dgm.description = 'Tank'
>> and spatial_ref.position_ = '2';
>
> Is spatial_ref.position_ text? If it's an integer, drop the quotes.
>
> -- Andy
>
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