Hello, I use the raster package for asci files it works great and has a very hands on access to get statistics or do any kind of raster operations hth a
MSc. Alexander Arpaci Assistant researcher Department of Forest - and Soil Sciences Institute of Silviculture Tel. +43-1-47654-4081 e-mail: alexander.arp...@boku.ac.at www.wabo.boku.ac.at >>> Micha* Kwieci*ski 26.08.11 15.41 Uhr >>> Hi, I am having difficulty in reading data for further use that is in ASCII grid format (it's the UN population data from http://sedac.ciesin.columbia.edu/gpw). I used readGDAL function which leaves me with SpatialGridDataFrame class object, but apart from creating simple image with map = readGDAL("eur.asc", region.dim=c(889,1050), output.dim=c(889,1050)) image(map, col=topo.colors(256, alpha=1)) , I have no clue how to operate on this object. All I can see it contains x and y coordinates, but any head() or summary() does not provide me with information on how to refer to the actual data that ASCII grid contains. And yet the image can be generated properly, so the data obviously is somewhere there! I can see I theoretically should find something under map["z"], but all I have is an error: Error in `[.data.frame`(x@data, , i, drop = FALSE) : undefined columns selected Or entire problem may be stated in terms of question: how do I set colours for map like that ( http://sedac.ciesin.columbia.edu/gpw/maps/poldens.pdf )? (let's say I want to manually set intervals for colouring the variable that is in the grid file) This is not the goal of my work with this data, but I believe the solution do this problem has very much in common with general operations on data from ascii grid file. Disregarding the need to create beautiful maps, I can always try to use read.table (oh, wait, the 5 MB bit freezes my R) and then use this data for other complex spatial calculations that require also other data to be combined with data from grid, but right now my problem is just as specified above. Or maybe I should have used something else than readGDAL? I am using R2.9.2, as any later version leaves me with blank output instead of the image I want. Don't know the reason for it, but I thought I will stay with the version that works instead of unnecessary troubleshooting. I also wrote a program in C that extracted the europe part of the world data, so that my ASCII file is 5 MB instead of 117 MB, but it appears to be OK, so I don't think the problem lies here. _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo