[R-sig-Geo] Problem with aggregating UScensus2000 FL data

Ista Zahn izahn at psych.rochester.edu
Wed Aug 3 13:45:57 CEST 2011 

On Wed, Aug 3, 2011 at 7:24 AM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> On Mon, 1 Aug 2011, Roger Bivand wrote:
>
>> On Mon, 1 Aug 2011, Ista Zahn wrote:
>>
>>> Hi Roger,
>>>
>>> On Mon, Aug 1, 2011 at 2:38 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>>>>
>>>> On Mon, 1 Aug 2011, Ista Zahn wrote:
>>>>
>>>>> Oops, I got the examples mixed up. The Alabama example works, the
>>>>> Florida example does not. I also should have given the version info,
>>>>> as this may well be version specific.
>>>>
>>>> You also need to provide the link to the data file, and the code prior
>>>> to
>>>> what you show. The function county() is not defined anywhere,
>>>> consequently
>>>> the attribute fields are nothing like tract boundaries such as those on:
>>>
>>> Sorry I wasn't clear. The data and the county function are in the
>>> UScensus2000 packages. Let me try again. A complete example leading to
>>> the error is
>>>
>>> library(UScensus2000)
>>
>> Perhaps contact the package maintainer? It is very possible that the
>> package ships with unclean topologies, isn't it? I'll try to look later.
>
> library(UScensus2000)
> library(maptools)
> data(countyfips)
> tmp <- county(fips = gsub("^..", "", countyfips$fips[countyfips$acronym ==
> "fl"]), state = "fl", level = "tract")
> dat <- as.data.frame(tmp)
> tmp.county <- unionSpatialPolygons(tmp, dat$county)
> # fails on (-82.6787 28.4335) == (-82.6787 28.4335)
> getScale()
> setScale(1e+09)
> tmp.county <- unionSpatialPolygons(tmp, dat$county)
> # works
>
> The issue is that GEOS assumes that it is working on planar coordinates, and
> allows plenty of trailing significant digits before truncating. With
> geographical coordinates, the nth trailing digit may be the one that
> disambiguates two points. Increasing the scale by one order of magnitude is
> sufficient in this case. I do not see the coordinates you stated initially.

Ah! Yes, I am enlightened. Thank you Roger.

-Ista

>
> Roger
>
>>
>> Roger
>>
>>> library(maptools)
>>> data(countyfips)
>>>
>>> tmp <- county(fips = gsub("^..", "",
>>> countyfips$fips[countyfips$acronym == "fl"]), state = "fl", level =
>>> "tract")
>>> dat <- as.data.frame(tmp)
>>> tmp.county <- unionSpatialPolygons(tmp, dat$county)
>>>
>>>>
>>>> http://www.census.gov/geo/www/cob/tr2000.html
>>>>
>>>> The lines do intersect (touch), and should not in a topologically
>>>> correct
>>>> setting; the coordinates seem odd - what is the projection? Did you run
>>>> checkPolygonsHoles() first?
>>>
>>> I would if I could figure out how to convert a SpatialPolygons object
>>> to a Polygons object... I'm just getting started with sp.
>>>
>>> Thanks,
>>> Ista
>>>
>>>>
>>>> Roger
>>>>
>>>>>
>>>>> R version 2.13.1 (2011-07-08)
>>>>> Platform: i386-pc-mingw32/i386 (32-bit)
>>>>>
>>>>> locale:
>>>>> [1] LC_COLLATE=English_United States.1252
>>>>> [2] LC_CTYPE=English_United States.1252
>>>>> [3] LC_MONETARY=English_United States.1252
>>>>> [4] LC_NUMERIC=C
>>>>> [5] LC_TIME=English_United States.1252
>>>>>
>>>>> attached base packages:
>>>>> [1] grid      stats     graphics  grDevices utils     datasets  methods
>>>>> [8] base
>>>>>
>>>>> other attached packages:
>>>>> [1] rgeos_0.1-8             stringr_0.5             quadprog_1.5-4
>>>>> [4] directlabels_1.3        UScensus2000_1.00       gpclib_1.5-1
>>>>> [7] UScensus2000cdp_0.03    UScensus2000blkgrp_0.03
>>>>> UScensus2000tract_0.03
>>>>> [10] rgdal_0.7-1             maptools_0.8-9          lattice_0.19-30
>>>>> [13] sp_0.9-84               foreign_0.8-45          ggplot2_0.8.9
>>>>> [16] proto_0.3-9.2           reshape_0.8.4           plyr_1.5.2
>>>>>
>>>>> loaded via a namespace (and not attached):
>>>>> [1] digest_0.5.0 tools_2.13.1
>>>>>>
>>>>>
>>>>> On Mon, Aug 1, 2011 at 11:09 AM, Ista Zahn <izahn at psych.rochester.edu>
>>>>> wrote:
>>>>>>
>>>>>> Hi all,
>>>>>> I am trying to aggregate the UScensus data for Florida up to the zip
>>>>>> code level using unionSpatialPolygons from the maptools package. This
>>>>>> works for other states, but not for Florida:
>>>>>>
>>>>>> ## Works
>>>>>> tmp <- county(fips = gsub("^..", "",
>>>>>> countyfips$fips[countyfips$acronym == "fl"]), state = "fl", level =
>>>>>> "tract")
>>>>>> dat <- as.data.frame(tmp)
>>>>>> tmp.county <- unionSpatialPolygons(tmp, dat$county)
>>>>>>
>>>>>> ## Returns error
>>>>>> tmp <- county(fips = gsub("^..", "",
>>>>>> countyfips$fips[countyfips$acronym == "al"]), state = "al", level =
>>>>>> "tract")
>>>>>> dat <- as.data.frame(tmp)
>>>>>> tmp.county <- unionSpatialPolygons(tmp, dat$county)
>>>>>> Error in TopologyFunc(groupID(spgeom[ids[[i]]], id[ids[[i]]]),
>>>>>> names(ids)[i],  :
>>>>>>  TopologyException: found non-noded intersection between LINESTRING
>>>>>> (-0.640183 0.433522, -0.678743 0.433456) and LINESTRING (-0.678743
>>>>>> 0.433456, -0.677839 0.434367) at -0.678743 0.433456
>>>>>>
>>>>>> Does anyone have a suggestion about how to do this?
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> Ista
>>>>>> --
>>>>>> Ista Zahn
>>>>>> Graduate student
>>>>>> University of Rochester
>>>>>> Department of Clinical and Social Psychology
>>>>>> http://yourpsyche.org
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> Roger Bivand
>>>> Department of Economics, NHH Norwegian School of Economics,
>>>> Helleveien 30, N-5045 Bergen, Norway.
>>>> voice: +47 55 95 93 55; fax +47 55 95 95 43
>>>> e-mail: Roger.Bivand at nhh.no
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
> --
> Roger Bivand
> Department of Economics, NHH Norwegian School of Economics,
> Helleveien 30, N-5045 Bergen, Norway.
> voice: +47 55 95 93 55; fax +47 55 95 95 43
> e-mail: Roger.Bivand at nhh.no
> _______________________________________________
> R-sig-Geo mailing list
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>
>



-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org

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