[postgis-users] How do you do neighborhood functions?

[collin]

Greetings folks,

Question:  I would like to find the average height (z2) of all the 
points within 10 meters of every point.  Any ideas on how to do this?
I have point data from lidar (snippet below).  I made point geometry 
from the raw data. 
           time      |          x2         |          y2       |      
z2   |  int2 |                      geom2
       
-------------+-----------------+----------------+---------+------+-------------------------------------------------
161626.12404 | 10568414.29 |      4247026 | 388.2   |   75 | 
SRID=32610;POINT(10568414.29 4247026 388.2)
161626.12407 | 10568414.31 |      4247026 | 388.26 |   74 | 
SRID=32610;POINT(10568414.31 4247026 388.26)
161626.1241   | 10568414.33 | 4247026.01 | 388.33 |   75 | 
SRID=32610;POINT(10568414.33 4247026.01 388.33)

I tried
    UPDATE napatest SET z2avg10 = avg(z2) 
    WHERE point_inside_circle(geom_point_first, xf, yf, 10);
but this only updated a single row.  z2avg10 is a new field I had added.

Is there a standard method for performing neighborhood functions? i.e. 
any set of statistics for each and every row about their neighboring points.

thanks in advance,

Collin
GIS informatics researcher, UC Berkeley