On Thu, Feb 4, 2010 at 4:03 AM, karine heerah <karine.hee...@hotmail.fr> wrote: > > Hi everybody. > > > > i have 2 datasets : one with a long grid a lat grid and a bathymetry grid > > the second one only has the long and lat coordinates. > > So i want to know the bathymetry associated to the second dataset. I thought > it was a good idea to do an interpolation between the two datasets. I find a > script doing that on matlab but i want to do it on R. Do you how to do it? > > > > for ii = 1:length(seal_dive_depth07) > > seal_bathy_depth07(ii) = > interp2(long,latg,A,seal_lon07(ii),seal_lat07(ii)); > end > > > > Karine HEERAH
There are several interpolation routines available that will take you between these two grids. The ones I used when preparing bathymetry data for SWAN and ADCIRC models were: >From the fields package: regular grid to regular grid -> interp.surface.grid() regular grid to irregular grid -> interp.surface() >From the akima package: irregular grid to regular grid -> interp() As far as I recall, each of these routines uses either bilinear or bicubic interpolation. The routine as.image() may help you organize your data into the input forms required by these functions. The "sp" package may also help you handle the spatial nature of the data. "sp" contains a routine called as.image.SpatialGridDataFrame() that performs the same function as as.image() on spatially gridded data. There are several other packages available that implement methods other than bilinear/cubic interpolation such as kriging, but I don't have any first hand experience with them. Hope this helps! -Charlie ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
