Math Operators

[Bob Pawley]

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Hi

 

I have an expression such as -

 

select ST_distance(st_centroid(p_id.p_id.the_geom), st_boundary(p_id.p_id.the_geom))/2 + 15000
   from p_id.p_id
   where p_id.p_id.process_id = '1012' ;

 

This works

 

I can access the number 15000 from a table as a variable. 

 

I want to be able to also access the + (or -) from a table as a variable but can't figure out how to do this.

 

Is it possible to store math operators and access them from a table??

 

Bob

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[Michael Smedberg-2]

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Could you store the numbers "1" and "-1", and then do

 

+ (one_or_minus_one * 15000)

 

That is, subtraction is the same as addition of the negative?

---

From: postgis-users-bounces@... [mailto:postgis-users-bounces@...] On Behalf Of Bob Pawley
Sent: Wednesday, July 01, 2009 11:35 AM
To: PostGIS Users Discussion
Subject: [postgis-users] Math Operators

 

Hi

 

I have an expression such as -

 

select ST_distance(st_centroid(p_id.p_id.the_geom), st_boundary(p_id.p_id.the_geom))/2 + 15000
   from p_id.p_id
   where p_id.p_id.process_id = '1012' ;

 

This works

 

I can access the number 15000 from a table as a variable. 

 

I want to be able to also access the + (or -) from a table as a variable but can't figure out how to do this.

 

Is it possible to store math operators and access them from a table??

 

Bob

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[Sean Fulton]

It's not clear what you're trying to do but can you simply store the
15000 as positive or negative?  Then you always add.  Adding a
negative is same as subtracting.

  Sean


On Jul 1, 2:35 pm, "Bob Pawley" <rjpaw...@...> wrote:

> Hi
>
> I have an expression such as -
>
> select ST_distance(st_centroid(p_id.p_id.the_geom), st_boundary(p_id.p_id.the_geom))/2 + 15000
>    from p_id.p_id
>    where p_id.p_id.process_id = '1012' ;
>
> This works
>
> I can access the number 15000 from a table as a variable.
>
> I want to be able to also access the + (or -) from a table as a variable but can't figure out how to do this.
>
> Is it possible to store math operators and access them from a table??
>
> Bob
>
> _______________________________________________
> postgis-users mailing list
> postgis-us...@...://postgis.refractions.net/mailman/listinfo/postgis-users

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