[Raster-commits] r218 - in pkg/raster: R man

[noreply at r-forge.r-project.org]

Author: rhijmans
Date: 2009-01-30 06:51:03 +0100 (Fri, 30 Jan 2009)
New Revision: 218

Added:
   pkg/raster/R/makeProjString.R
Modified:
   pkg/raster/man/project.Rd
Log:


Added: pkg/raster/R/makeProjString.R
===================================================================
--- pkg/raster/R/makeProjString.R	                        (rev 0)
+++ pkg/raster/R/makeProjString.R	2009-01-30 05:51:03 UTC (rev 218)
@@ -0,0 +1,57 @@
+# Author: Robert J. Hijmans, r.hijmans at gmail.com
+# International Rice Research Institute
+# Date :  January 2009
+# Version 0.8
+# Licence GPL v3
+
+
+
+makeProj <- function(projection='longlat', ..., ellipsoid="", datum="WGS84", asText=TRUE) {
+	prj <- projInfo("proj")
+	ell <- projInfo("ellps")
+	dat <- projInfo("datum")
+	projection <- trim(projection)
+	ellipsoid <- trim(ellipsoid)
+	datum <- trim(datum)
+	if (!(projection %in% prj[,1])) {
+		stop("unknown projection. See projInfo()") 
+	} else {
+		pstr <- paste('+proj=',projection, sep="")
+		projname <- as.vector(prj[which(prj[,1]==projection), 2])
+	}
+	pargs <- list(...)
+	for (i in 1:length(pargs)) {
+		pstr <- paste(pstr, ' +', pargs[[i]], sep="")
+	}
+	if (ellipsoid != "") {
+		if (!(ellipsoid %in% ell[,1])) { 
+			stop("unknown ellipsoid. See projInfo('ellps')") 
+		} else {
+			pstr <- paste(pstr, " +ellps=", ellipsoid, sep="")
+#			ellipname <- ell[which(ell[,1]==ellipsoid), 2]
+		}
+	}
+	if (datum != "") {
+		if (!(datum %in% dat[,1])) { 
+			stop("unknown datum. See projInfo('datum')") 
+		} else {
+			pstr <- paste(pstr, " +datum=", datum, sep="")
+#			datumname <- as.vector(dat[which(dat[,1]==datum), 2])
+		}
+	}
+	
+	cat("Projection: ", projname[1], "\n")
+	
+	crs <- newCRS(pstr)
+
+		
+	if (asText) { 
+		return(trim(crs at projargs))
+	} else {
+		return(crs)
+	}
+}
+
+ #newprj2 <- makeProj("lcc", "lat_1=48", "lat_2=33", "lon_0=-100", asText=T)
+
+

Modified: pkg/raster/man/project.Rd
===================================================================
--- pkg/raster/man/project.Rd	2009-01-30 03:31:38 UTC (rev 217)
+++ pkg/raster/man/project.Rd	2009-01-30 05:51:03 UTC (rev 218)
@@ -1,14 +1,16 @@
 \name{project}
 \alias{projectRaster}
 \alias{projectBbox}
+\alias{makeProj}
 
 \title{Change the projection of a RasterLayer}
 \description{
-	Change the projection of a RasterLayer
+	Change the projection of a RasterLayer. 
 }
 \usage{
 projectRaster(from, to, method="nngb", overwrite=FALSE)
 projectBbox(object, projstring)
+makeProj(projection='longlat', ..., ellipsoid="", datum="WGS84", asText=TRUE) 
 }
 
 \arguments{
@@ -18,10 +20,17 @@
   \item{overwrite}{}
   \item{object}{}
   \item{projstring}{}
+  \item{projection}{}
+  \item{...}{parameters for the projection}  
+  \item{ellipsoid}{}
+  \item{datum}{}  
+  \item{asText}{logical. If \{code}{FALSE}, an object of class 'CRS' will be returned.}  
 }
 
 \details{
  first create projected bbox (in BasicRaster object). Then project. 
+ makeProj is a helper function to create a valid PROJ.4 string or CRS object. 
+ See projInfo('proj'), projInfo('ellps'), and projInfo('datum') for valud choices
 }
 
 \value{
@@ -35,6 +44,9 @@
 r <- setValues(r, 1:ncell(r))
 # proj.4 projection description
 newproj <- "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100"
+# this is equivalent to
+newproj2 <- makeProj("lcc", "lat_1=48", "lat_2=33", "lon_0=-100", ellp="WGS84", datum="")
+
 # create a new RasterLayer with a BoundingBox with the new projection
 projras <- projectBbox(r, newproj)
 # Adjust the cell size