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, <jin...@ga.gov.au> 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
> ____________________________________________________________
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