Re: [postgis-users] Calculate Average Distance (w/ LIMIT)

2011-01-03 Thread Ben Madin 
Andreas,

I can't improve on Nicolas' suggestion, but at a guess you might also want to 
look at the spatstat package in R, which has defined a number of functions for 
this sort of analysis, and can include windows (ie country polygons) to 
incorporate edge correction - ie F, G and K functions.

cheers

Ben


On 03/01/2011, at 9:05 PM, Nicolas Ribot wrote:

> On 6 December 2010 13:19, Andreas Forø Tollefsen  wrote:
>> Hi all.
>> I have two point data sets. One point set is health observations, the other
>> one is conflicts.
>> What i want to do is to calculate the average distance from each health
>> observation to the 10 nearest conflict points.
>> I have managed to calculate the average distance, but only to all conflict
>> points.
>> My query:
>> select "LBGE51FL".the_geom, "LBGE51FL".gid,
>> AVG(ST_Distance(ST_Transform("LBGE51FL".the_geom, 954010),
>> ST_Transform(acled.the_geom, 954010)))/1000 AS dist INTO LB_dist FROM
>> "LBGE51FL", acled WHERE acled.gwno = 450 GROUP BY "LBGE51FL".the_geom,
>> "LBGE51FL".gid;
>> SRID 954010 is Eckert VI.
>> Any idea on how to limit this query to the 10 nearest points?
>> Thanks.
>> Andreas
> 
> Hi,
> 
> Using a subquery to compute the distance, order by distance, limit 10,
> before computing the avg distance ?
> 
> Nicolas
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Re: [postgis-users] Calculate Average Distance (w/ LIMIT)

2011-01-03 Thread Nicolas Ribot 
On 6 December 2010 13:19, Andreas Forø Tollefsen  wrote:
> Hi all.
> I have two point data sets. One point set is health observations, the other
> one is conflicts.
> What i want to do is to calculate the average distance from each health
> observation to the 10 nearest conflict points.
> I have managed to calculate the average distance, but only to all conflict
> points.
> My query:
> select "LBGE51FL".the_geom, "LBGE51FL".gid,
> AVG(ST_Distance(ST_Transform("LBGE51FL".the_geom, 954010),
> ST_Transform(acled.the_geom, 954010)))/1000 AS dist INTO LB_dist FROM
> "LBGE51FL", acled WHERE acled.gwno = 450 GROUP BY "LBGE51FL".the_geom,
> "LBGE51FL".gid;
> SRID 954010 is Eckert VI.
> Any idea on how to limit this query to the 10 nearest points?
> Thanks.
> Andreas

Hi,

Using a subquery to compute the distance, order by distance, limit 10,
before computing the avg distance ?

Nicolas
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[postgis-users] Calculate Average Distance (w/ LIMIT)

2010-12-06 Thread Andreas Forø Tollefsen 
Hi all.

I have two point data sets. One point set is health observations, the other
one is conflicts.
What i want to do is to calculate the average distance from each health
observation to the 10 nearest conflict points.
I have managed to calculate the average distance, but only to all conflict
points.

My query:
select "LBGE51FL".the_geom, "LBGE51FL".gid,
AVG(ST_Distance(ST_Transform("LBGE51FL".the_geom, 954010),
ST_Transform(acled.the_geom, 954010)))/1000 AS dist INTO LB_dist FROM
"LBGE51FL", acled WHERE acled.gwno = 450 GROUP BY "LBGE51FL".the_geom,
"LBGE51FL".gid;

SRID 954010 is Eckert VI.

Any idea on how to limit this query to the 10 nearest points?

Thanks.

Andreas
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