Just for the record. this is how I would do this with the raster package (Kamran's example should work, but seems a bit unnecessarily complex; just what we are trying to avoid with that package :):
install.packages("raster", repos="http://R-Forge.R-project.org") library(raster) xy <- your matrix raster <- rasterFromFile("C:/yourfile") v <- xyValues(raster, xy) xyv <- cbind(xy, v) Robert On Tue, Mar 10, 2009 at 7:50 PM, Paul Hiemstra <p.hiems...@geo.uu.nl> wrote: > Hi, > > Funny to see how you can do things in multiple ways in R :). To add to the > possibilities, you could probably also get this functionality using R and > Grass. > > I would personally recommend to use overlay() as you don't have to install > anything apart from the sp package, unlike using rsaga and SAGA. Especially > if the only thing you want is to do an overlay. When there was other SAGA > specific functionality you needed, SAGA would be a good option. In addition > to not having to install a lot of software, overlay() has been used > extensively, this in contrast to the raster package which is still > experimental. But this is strictly my personal opinion ofcourse :). > > cheers, > Paul > > Kamran Safi Radolfzell wrote: >> >> Hi all, >> >> the raster package is although in its alpha stage very helpful in this >> respect: >> >> install.packages("raster", repos="http://R-Forge.R-project.org") >> library(raster) >> library(maptools) >> X <- Y <- raster <- rasterFromFile("C:/yourfile") >> (result <- data.frame(Long=x, Lat=y, Value=xyValues(raster, matrix(c(x,y), >> ncol=2))))) >> >> >> That should work. Remember to take out the install.package after initial >> install. Of course you can work with several coordinates. Peadagogically >> better is the overlay() function... >> >> Very straight forward. >> Kami >> >> On Tue, 10 Mar 2009 11:04:23 +0100, Paul Hiemstra wrote >> >>> >>> Hi, >>> >>> An option using only R is to use the overlay() command from the sp >>> package, try running this example: >>> >>> # Load data >>> library(sp) >>> data(meuse) >>> # point data >>> coordinates(meuse) = ~x+y >>> data(meuse.grid) >>> # grid data >>> gridded(meuse.grid) = ~x+y >>> >>> overlay(meuse.grid, meuse) >>> # Returns the indices in meuse.grid correpsonding to the points in meuse >>> # get the data from meuse.grid, for example the column "dist" >>> # a non spatial vector >>> dist = meuse.grid$dist[overlay(meuse.grid, meuse)] >>> # A spatialPointsDataFrame >>> dist = meuse.grid[overlay(meuse.grid, meuse), "dist"] >>> >>> Also check out the rgdal pacakge to get your data into R-spatial objects. >>> >>> cheers, >>> Paul >>> >>> Frauke Barthold wrote: >>> >>>> >>>> Dear list, >>>> >>>> I have a soilmap as an Ascii grid and a dataframe with x and y >> >> coordinates (these are sampling points). I would now like to extract >> values from the soilmap to the dataframe based on location, the x and y >> values. Is there any way to do this in R? >> >>>> >>>> Cheers, >>>> Frauke >>>> _________________________________________________________________ >>>> >>>> >>>> [[alternative HTML version deleted]] >>>> >>>> _______________________________________________ >>>> R-sig-Geo mailing list >>>> R-sig-Geo@stat.math.ethz.ch >>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>>> >>>> >>> >>> -- >>> Drs. Paul Hiemstra >>> Department of Physical Geography >>> Faculty of Geosciences >>> University of Utrecht >>> Heidelberglaan 2 >>> P.O. Box 80.115 >>> 3508 TC Utrecht >>> Phone: +3130 274 3113 Mon-Tue >>> Phone: +3130 253 5773 Wed-Fri >>> http://intamap.geo.uu.nl/~paul >>> >>> _______________________________________________ >>> R-sig-Geo mailing list >>> R-sig-Geo@stat.math.ethz.ch >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>> >> >> >> -- >> Open WebMail Project (http://openwebmail.org) >> >> > > > -- > Drs. Paul Hiemstra > Department of Physical Geography > Faculty of Geosciences > University of Utrecht > Heidelberglaan 2 > P.O. Box 80.115 > 3508 TC Utrecht > Phone: +3130 274 3113 Mon-Tue > Phone: +3130 253 5773 Wed-Fri > http://intamap.geo.uu.nl/~paul > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo