[R-sig-Geo] how to filter a shapefile ?

[Arnald Marcer]

Thank you very much Roger.

Still another question: Can you plot a polygon shapefile with borders 
but transparent interiors ?

Arnald Marcer
CREAF

On 09/16/2010 02:10 PM, Roger Bivand wrote:
> On Thu, 16 Sep 2010, Mayeul KAUFFMANN wrote:
>
>> You can read your shapefile with:
>> library(rgdal)
>> countries_spdf <- readOGR(dsn=root_path, 
>> "countries_file_without_extension")
>> #You'll have a spatial point data frame with marks. Look at 
>> str(countries_spdf).
>> Try:
>> plot(countries_spdf[countries_spdf at data$AREA>1000])
>
> Correct, subset with the "[" method as with data.frame objects. But 
> avoid using the data slot directly, use the "$" method as with 
> data.frame objects:
>
> plot(countries_spdf[countries_spdf$AREA>1000,])
>
> and insert a comma in the "[" method to choose the rows matching the 
> condition:
>
> library(rgdal)
> dsn <- system.file("vectors", package = "rgdal")[1]
> scot_BNG <- readOGR(dsn=dsn, layer="scot_BNG")
> plot(scot_BNG, border="grey")
> plot(scot_BNG[scot_BNG$SMR > 100,], border="black", lwd=2, add=TRUE)
>
> Hope this helps,
>
> Roger
>
>
>> Mayeul
>> _____________________________________________________
>> Dr. Mayeul KAUFFMANN, Conflict Specialist
>> European Commission, Joint Research Centre (JRC)
>> Institute for the Protection and Security of the Citizen (IPSC)
>> Global Security and Crisis Management - ISFEREA
>> Via E. Fermi 2749 - I-21027 Ispra (VA), ITALY
>> Phone: (+39) 033278 5071
>> http://isferea.jrc.ec.europa.eu/Staff/Pages/Kauffmann-Mayeul.aspx
>>
>> (Office: building 48c, 1st floor, room 123. TP: 483)
>>
>> _____________________________________________________
>> Dr. Mayeul KAUFFMANN, Conflict Specialist
>> European Commission, Joint Research Centre (JRC)
>> Institute for the Protection and Security of the Citizen (IPSC)
>> Global Security and Crisis Management - ISFEREA
>> Via E. Fermi 2749 - I-21027 Ispra (VA), ITALY
>> Phone: (+39) 033278 5071
>> http://isferea.jrc.ec.europa.eu/Staff/Pages/Kauffmann-Mayeul.aspx
>>
>> (Office: building 48c, 1st floor, room 123. TP: 483)
>>
>>
>> -----Original Message-----
>> From: r-sig-geo-bounces at stat.math.ethz.ch
>> [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of Arnald Marcer
>> Sent: Thursday, September 16, 2010 12:58 PM
>> To: r-sig-geo
>> Subject: [R-sig-Geo] how to filter a shapefile ?
>>
>> Hi,
>>
>> Can anyone give me a hint on how to extract/filter/subset
>> polygons from a shapefile based on an attribute of its dbf
>> table ?
>>
>> Example:
>>
>> shapefile: world.shp
>> attributes of its dbf table: ID, AREA, COUNTRY, ...
>>
>> How can I plot a shapefile with only countries above a certain AREA 
>> value ?
>>
>> Thank you very much,
>>
>> Arnald Marcer
>> CREAF
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
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>>
>


-- 
-----------------------------------------------------------------
Arnald Marcer
Investigador

Centre de Recerca Ecològica i Aplicacions Forestals (CREAF)
Universitat Autònoma de Barcelona
08193 Barcelona

Tel: 93 5811312
Fax: 93 5814151
-----------------------------------------------------------------
Arnald Marcer
Researcher

Centre for Ecological Research and Forestry Applications (CREAF)
Autonomous University of Barcelona
08193 Barcelona

Phone: +34 93 5811312
Fax:   +34 93 5814151