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_s...@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-boun...@stat.math.ethz.ch
[mailto:r-sig-geo-boun...@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
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--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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