On Wed, Oct 3, 2012 at 9:20 PM, wrote: > ** ** ** ** ** ** > > Hi Robert,**** > > Thank you very much for the reply. Both datasets are in txt format. Lat > and long are in WGS84. So I might need to do something like:**** > > library(raster)**** > > p <- read.table('points.txt')**** > > d <- read.table('gridcells.txt')**** > > r <- rasterFromPoints(d)**** > > values<- extract(r, p)**** > > ** ** > > Is anything else I should add or modify? rasterFromPoints seems not > available in raster 2.0-05. > Sorry, I misspoke, I should have said "rasterFromXYZ" I still do not know what "d" looks like. "txt format" is not very descriptive, but if it regular spaced points, something like x, y, z 1, 2, 3, 1, 3, 5 then you can probably do what you write above, using rasterFromXYZ instead of rasterFromPoints Robert **** > > ** ** > > What I intend to do is extract and add lat/long of corresponding grid > cells to my points dataset as below:**** > > > points**** > > lat.sample long.sample lat.gridcell long.gridcell **** > > 1 -21.258000 110.502000**** > > 2 -42.609683 144.412700**** > > 3 -36.733000 132.050000**** > > 4 -21.330000 110.482000**** > > 5 -13.156840 136.757080**** > > 6 -14.633000 117.967000**** > > 7 -23.502580 111.083450**** > > 8 -15.674870 138.058400**** > > 9 -12.650000 136.950000**** > > 10 -9.955000 143.806667**** > > ** ** > > All the best,**** > > Jin**** > ------------------------------ > > *From:* Robert J. Hijmans [mailto:r.hijmans@gmail.com] > *Sent:* Thursday, 4 October 2012 1:13 PM > *To:* **Li Jin** > *Cc:* **r-sig-geo@r-project.org** > *Subject:* Re: [R-sig-Geo] Extract location information from grid cells > for sample points [SEC=UNCLASSIFIED]**** > > ** ** > > Hi Jin, **** > > ** ** > > From your description it is not entirely clear what your input data looks > like. But you can something like this**** > > ** ** > > library(raster)**** > > p <- read.table('points.txt')**** > > r <- raster('file.asc')**** > > values<- extract(r, p)**** > > ** ** > > Perhaps you need to subset "p" to get the appropriate columns representing > longitude and latitude (in that order). Or perhaps your grid data is not > really in a 'raster' format? I am not sure from your description. In that > case you may need to to**** > > ** ** > > d <- read.table('file.asc')**** > > r <- rasterFromPoints(d)**** > > ** ** > > You may also want to check out functions cellFromXY to link coordinates to > cells in a raster.**** > > ** ** > > All the best, Robert**** > > ** ** > > On Wed, Oct 3, 2012 at 5:38 PM, wrote:**** > > Dear list, > > I have two datasets: one is for point samples with lat and long > information at accuracy of 0.001 degrees. Another is grid cells at a > resolution of 0.0025 degrees. Both datasets are in txt format. Now I need > to extract the lat and long information from the grid cell dataset for the > point samples by assigning the lat and long of a grid cell to a sample > point that falls in the grid cell. I usually get this done in ArcGIS. I was > wondering if it is possible in R. I searched but failed to find a right > function to implement this in R. > > Many thanks for any suggestions. > > Regards, > > Jin Li > Spatial Modeller/Computational Statistician | Coastal, Marine and > Climate Change Group > Environmental Geoscience Division | GEOSCIENCE ****AUSTRALIA**** > ____________________________________________________________ > Phone: +61 2 6249 9899 <%2B61%202%206249%209899> Fax: +61 2 6249 9999 > Email: Jin.Li@ga.gov.au Web: www.ga.gov.au< > http://www.ga.gov.au/> > ****Cnr Jerrabomberra Avenue**** and ****Hindmarsh Drive**** Symonston ACT > GPO Box 378 **Canberra** ACT 2601 ****Australia**** > Applying geoscience to ****Australia****'s most important challenges > > > Geoscience ****Australia**** Disclaimer: This e-mail (and files > transmitted with it) is intended only for the person or entity to which it > is addressed. 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