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Amit Kulkarni | 1 Mar 2006 19:20
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Re: quantiles, quartiles, or jenks natural

Sorry, I have been catching up on the past few months emails. I just
want to add that I read that quantiles and minimum boundary error are
better than jenks. Also minimum boundary error takes into account the
underlying topology.

The two being better are mentioned in 

Brewer, Cynthia A. & Pickle, Linda (2002) Evaluation of Methods for
Classifying Epidemiological Data on Choropleth Maps in Series.
Annals of the Association of American Geographers 92 (4), 662-681

And the minimum boundary algorithm is supposedly mentioned in 

Cromley, E. K. , and R. G. Cromley. 1996. An analysis of alternative
classification  schemes  for  medical  atlas mapping. European Journal
of Cancer 32A (9): 1551 -- 59. 

Cromley, R. G. , and R. D. Mrozinski. 1999. The classification of
ordinal data for choropleth mapping. The Cartographic Journal 36 (2):
101 -- 9.

HTH,
amit

Date: Tue, 14 Feb 2006 12:38:39 -0800
From: Paul Ramsey <pramsey <at> refractions.net>

I did some in PHP, but the algorithms are relatively braindead, the  
quantile stuff in particular.  Jenks I did some research on but never  
really found a definitive description of the process.  Some of the
(Continue reading)

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Robert Burgholzer | 2 Mar 2006 15:40

RE: quantiles, quartiles, or jenks natural

OK,
I'm coming into this late, but I am a user of PL/R and PostGIS, and
would appreciate any progress on developing some classification routines
to be posted to this lists, or I would be interested in being notified
offline.

Thanks!

r.b.

-----Original Message-----
From: postgis-users-bounces <at> postgis.refractions.net
[mailto:postgis-users-bounces <at> postgis.refractions.net] On Behalf Of Amit
Kulkarni
Sent: Wednesday, March 01, 2006 1:20 PM
To: postgis-users <at> postgis.refractions.net
Subject: Re: [postgis-users] quantiles, quartiles, or jenks natural

Sorry, I have been catching up on the past few months emails. I just
want to add that I read that quantiles and minimum boundary error are
better than jenks. Also minimum boundary error takes into account the
underlying topology.

The two being better are mentioned in 

Brewer, Cynthia A. & Pickle, Linda (2002) Evaluation of Methods for
Classifying Epidemiological Data on Choropleth Maps in Series.
Annals of the Association of American Geographers 92 (4), 662-681

And the minimum boundary algorithm is supposedly mentioned in
(Continue reading)

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David Bitner | 2 Mar 2006 15:57
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Re: quantiles, quartiles, or jenks natural

I ended up jumping into the PL/R world and just created an aggregate
wrapper around kmeans to get my class values. They ended up being
very, very close (identical in some cases) to classifications that had
been done with Jenks Natural Breaks.  If you want the same results
every time you run a classification on the same data, you need to set
the same seed value for the random number generator before each run.

It's pretty basic and my code is ugly due to some R parser errors that
I could only get passed by throwing all the code on one line with no
spaces (hey it worked and I didn't have time to look into the parser
error), but I can throw the code up if anyone would like.

On 3/2/06, Robert Burgholzer <rburghol <at> chesapeakebay.net> wrote:
> OK,
> I'm coming into this late, but I am a user of PL/R and PostGIS, and
> would appreciate any progress on developing some classification routines
> to be posted to this lists, or I would be interested in being notified
> offline.
>
> Thanks!
>
> r.b.
>
> -----Original Message-----
> From: postgis-users-bounces <at> postgis.refractions.net
> [mailto:postgis-users-bounces <at> postgis.refractions.net] On Behalf Of Amit
> Kulkarni
> Sent: Wednesday, March 01, 2006 1:20 PM
> To: postgis-users <at> postgis.refractions.net
> Subject: Re: [postgis-users] quantiles, quartiles, or jenks natural
(Continue reading)

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Robert Burgholzer | 2 Mar 2006 16:24

RE: quantiles, quartiles, or jenks natural

David,
I am trying to develop a little library of PL/R-code, so I would really
appreciate it being posted to the listserv, or sent to me.

Thanks,
r.b.

-----Original Message-----
From: postgis-users-bounces <at> postgis.refractions.net
[mailto:postgis-users-bounces <at> postgis.refractions.net] On Behalf Of
David Bitner
Sent: Thursday, March 02, 2006 9:58 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] quantiles, quartiles, or jenks natural

I ended up jumping into the PL/R world and just created an aggregate
wrapper around kmeans to get my class values. They ended up being
very, very close (identical in some cases) to classifications that had
been done with Jenks Natural Breaks.  If you want the same results
every time you run a classification on the same data, you need to set
the same seed value for the random number generator before each run.

It's pretty basic and my code is ugly due to some R parser errors that
I could only get passed by throwing all the code on one line with no
spaces (hey it worked and I didn't have time to look into the parser
error), but I can throw the code up if anyone would like.

On 3/2/06, Robert Burgholzer <rburghol <at> chesapeakebay.net> wrote:
> OK,
> I'm coming into this late, but I am a user of PL/R and PostGIS, and
(Continue reading)

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Stephen Woodbridge | 2 Mar 2006 16:41
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Re: quantiles, quartiles, or jenks natural

David,

Please post it to the listserv, I would be interested also. I have yet 
to jump into PL/R but it is on my list to do.

Thanks,
   -Steve

David Bitner wrote:
> I ended up jumping into the PL/R world and just created an aggregate
> wrapper around kmeans to get my class values. They ended up being
> very, very close (identical in some cases) to classifications that had
> been done with Jenks Natural Breaks.  If you want the same results
> every time you run a classification on the same data, you need to set
> the same seed value for the random number generator before each run.
> 
> It's pretty basic and my code is ugly due to some R parser errors that
> I could only get passed by throwing all the code on one line with no
> spaces (hey it worked and I didn't have time to look into the parser
> error), but I can throw the code up if anyone would like.
> 
> On 3/2/06, Robert Burgholzer <rburghol <at> chesapeakebay.net> wrote:
> 
>>OK,
>>I'm coming into this late, but I am a user of PL/R and PostGIS, and
>>would appreciate any progress on developing some classification routines
>>to be posted to this lists, or I would be interested in being notified
>>offline.
>>
>>Thanks!
(Continue reading)

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Arnaud Lesauvage | 2 Mar 2006 16:44
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TopologyException

Hi list !

The following error is raised :

TopologyException: no outgoing dirEdge found 
(742602,5.08777e+006,5.08777e+006)
ERROR:  GEOS Intersection() threw an error!

when I try to run this statement :

SELECT DISTINCT(c1.handle) AS handle
FROM cells_temp AS c1
INNER JOIN cells_temp AS c2
ON (c1.cell_geometry && c2.cell_geometry AND c1.handle!=c2.handle
AND IsValid(c1.cell_geometry) AND IsValid(c2.cell_geometry)
AND Relate(c1.cell_geometry,c2.cell_geometry,'2********'))
WHERE Area(Intersection(c1.cell_geometry,c2.cell_geometry))>0.5

I wrote this query to get all the geometries that overlap with 
another geometry from the table (i.e. the surface of the 
intersection is greater than 0.5 square meters).

If I remove the Intersection(c1.cell_geometry,c2.cell_geometry), 
the query runs fine !
IsValid returns true for the entire table !

Does anyone have a hint about what is going on ?

Thanks a lot !
(Continue reading)

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strk | 2 Mar 2006 16:50
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Re: TopologyException

GEOS is still not fully robust.
I'm seeking for examples of such exceptions,
if you can produce the smallest possible dataset raising
the exception that'll help.

I'm working on this right now, and I have a single
real test (valid geoms raising an exception on overlay op)

--strk;

On Thu, Mar 02, 2006 at 04:44:01PM +0100, Arnaud Lesauvage wrote:
> Hi list !
> 
> The following error is raised :
> 
> TopologyException: no outgoing dirEdge found 
> (742602,5.08777e+006,5.08777e+006)
> ERROR:  GEOS Intersection() threw an error!
> 
> when I try to run this statement :
> 
> SELECT DISTINCT(c1.handle) AS handle
> FROM cells_temp AS c1
> INNER JOIN cells_temp AS c2
> ON (c1.cell_geometry && c2.cell_geometry AND c1.handle!=c2.handle
> AND IsValid(c1.cell_geometry) AND IsValid(c2.cell_geometry)
> AND Relate(c1.cell_geometry,c2.cell_geometry,'2********'))
> WHERE Area(Intersection(c1.cell_geometry,c2.cell_geometry))>0.5
> 
> I wrote this query to get all the geometries that overlap with
(Continue reading)

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Arnaud Lesauvage | 2 Mar 2006 17:36
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Re: TopologyException

strk <at> refractions.net a écrit :
> GEOS is still not fully robust.
> I'm seeking for examples of such exceptions,
> if you can produce the smallest possible dataset raising
> the exception that'll help.
> 
> I'm working on this right now, and I have a single
> real test (valid geoms raising an exception on overlay op)

Sure, here you are !
I paste the WKT here in case attachments don't work on this list :

cell_geometry
"POLYGON((742605.987032656 5087763.72510381,742599.903121688 
5087760.56016809,742598.666141033 
5087762.50894352,742591.100910753 
5087758.50480931,742586.861672536 
5087766.63211263,742591.417801844 
5087769.04526206,742592.428792606 
5087767.35034731,742601.541294342 
5087772.18101105,742605.987032656 5087763.72510381))"
"POLYGON((742601.541294537 5087772.18101068,742592.428792606 
5087767.35034731,742589.944404072 
5087771.51539701,742583.880455986 5087782.54873438,742582.81550675 
5087784.27809355,742583.216887765 5087784.43459684,742582.99081514 
5087785.0349637,742592.341351823 5087789.67654,742593.375823205 
5087787.7060691,742599.28794443 5087776.4640487,742601.541294537 
5087772.18101068))"

Regards
(Continue reading)

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Sears, Jeremy | 2 Mar 2006 17:40
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Favicon

old data loads but not new ...

Hi All,
Im having a problem with postgresql/postgis. We have been working with this
database for some time now. All of the tables that contain geometry have
been created in older versions of post (7 - 8.0). We have upgraded since
then and now use postgresql8.1 with updated postgis. Mapserver and Qgis can
connect to the older tables and display the geometry associated with them.
We have recently added a new spatial table, using what I understand to be
the same methodology that was used to add the other spatial tables. Neither
Mapserver nor Qgis can connect the this new table. The table is identical to
one of the older tables in everyway ( except the new table has different
records ). QGIS give the following error when I try to connect to the new
table:

..thetable has no primary key nor oid column...etc .. the table should be
indexed..

I have reindexed the database to no avail. Im relativly new to this so I am
hoping that someone on the list recoginizes this issue and can advise on
what to do. Any thoughts or suggestions would be great!

Thanks
Jeremy
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alex bodnaru | 2 Mar 2006 17:48
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Re: old data loads but not new ...


hi,

recent postgresql do not generate the oid column by default.
please check relevant issue on postgresql.org.

alex

Sears, Jeremy wrote:
> Hi All,
> Im having a problem with postgresql/postgis. We have been working with this
> database for some time now. All of the tables that contain geometry have
> been created in older versions of post (7 - 8.0). We have upgraded since
> then and now use postgresql8.1 with updated postgis. Mapserver and Qgis can
> connect to the older tables and display the geometry associated with them.
> We have recently added a new spatial table, using what I understand to be
> the same methodology that was used to add the other spatial tables. Neither
> Mapserver nor Qgis can connect the this new table. The table is identical to
> one of the older tables in everyway ( except the new table has different
> records ). QGIS give the following error when I try to connect to the new
> table:
> 
> ..thetable has no primary key nor oid column...etc .. the table should be
> indexed..
> 
> I have reindexed the database to no avail. Im relativly new to this so I am
> hoping that someone on the list recoginizes this issue and can advise on
> what to do. Any thoughts or suggestions would be great!
> 
> Thanks
(Continue reading)

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