[Biomod-commits] Importing georgraphical coordinates in R

[Wilfried Thuiller]

You have different way.
Either your data are already in a shapefile with associated coordinate files, or they are simply a txt files with coordinates and you know the projection system

1- Use the rgdal package.
library(rgdal)
poly <- readOGR("path_to_the_right_folder", layer="name_of_the_files_without_extension")
summary(poly)


2- In a text file you import in R with the name 'plots'
Let's say you use the WGS84 projections and the coordinates are in columns X_WGS84 and Y_WGS84
 pointsWGS84 <- plots[,c("X_WGS84", "Y_WGS84")]
 colnames(pointsWGS84) <- c("x","y")
 coordinates(pointsWGS84) <- c("x", "y")
### stipulate to R what is the projection. Look at the help file for proj4string
 proj4string(pointsWGS84) <- CRS("+proj=latlong +datum=WGS84") # WGS84 projection string
 head(pointsWGS84 at coords)

#if you want to transform the coordinates in another projection system. For instance here in Lambert for France II étendu.
# first create the projection file: 

proj4NTFII <- "+proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0 +k_0=0.99987742 +x_0=600000 +y_0=2200000 +a=6378249.2 +b=6356515 +towgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs"
  #EPSG Projection 27582 - NTF (Paris) / France II


pointsNTFII <- spTransform(pointsWGS84, CRS(proj4NTFII))
head(pointsNTFII at coords) 

You have most of the projection system here:

http://www.remotesensing.org/geotiff/proj_list/




Le 10 sept. 2010 à 22:36, Manuel Spínola a écrit :

> Dear list members,
> 
> How do I import data in geographical coordinates to R?
> 
> ref1                       ref2
> N10 41 08.7     W84 10 46.3
> N10 41 06.8     W84 10 46.4
> N10 41 06.4     W84 10 44.6
> N10 41 05.6     W84 10 46.0
> 
> Best,
> 
> Manuel
> 
> -- 
> Manuel Spínola, Ph.D.
> Instituto Internacional en Conservación y Manejo de Vida Silvestre
> Universidad Nacional
> Apartado 1350-3000
> Heredia
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> mspinola at una.ac.cr
> mspinola10 at gmail.com
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> 
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--------------------------
Dr. Wilfried Thuiller
Laboratoire d'Ecologie Alpine, UMR CNRS 5553
Université Joseph Fourier
BP53, 38041 Grenoble cedex 9, France
tel: +33 (0)4 76 51 44 97
fax: +33 (0)4 76 51 42 79

Email: wilfried.thuiller at ujf-grenoble.fr
Home page: http://www.will.chez-alice.fr
Website: http://www-leca.ujf-grenoble.fr/equipes/tde.htm

FP6 European MACIS project: http://www.macis-project.net
FP6 European EcoChange project: http://www.ecochange-project.eu





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