Dear list, thank you very much for all the many suggestions on how to extract values to points! I ended up using the RSAGA package with the pick.from.ascii.grid() function.
Cheers, Frauke > Date: Tue, 10 Mar 2009 20:19:17 +0800 > Subject: Re: [R-sig-Geo] extract values to points > From: r.hijm...@gmail.com > To: p.hiems...@geo.uu.nl > CC: ks...@mail.orn.mpg.de; r-sig-geo@stat.math.ethz.ch; > fkbarthol...@hotmail.com > > 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 > > _________________________________________________________________ [[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