[R-sig-Geo] Help with GIS

[Robert J. Hijmans]

After this:

> projras <- projectRaster(r0, pr)

You could also do plot(projras) or image(projras) and

v <- getValues(projras, format='matrix')

To get a matrix of values, with the advantage that values in this
matrix are organized as on the map (probably what you would expect),
which is different in matrix 'm' in Mike's example.

Robert

On Wed, Oct 27, 2010 at 2:16 PM, Michael Sumner <mdsumner at gmail.com> wrote:
> This is a dummy example - especially in terms of made up coordinate
> system details, but shows how you can reproject with the raster
> package:
>
> library(rgdal)
>
> ## create a grid, with dummy coordinates / projection
>
> im <- image2Grid(list(x = 1e5 * (1:nrow(volcano)), y = 1e5 *
> (1:ncol(volcano)), z = volcano), p4 = "+proj=laea")
>
> writeGDAL(im, "dummy.tif")
>
> ## now the process, using raster package
>
> library(raster)
>
>
> r0 <- raster("dummy.tif")
>
> # proj.4 projection description
> newproj <- "+proj=longlat +ellps=WGS84"
>
> pr <- projectExtent(r0, newproj)
> ## (optionally) Adjust the cell size
> ## res(pr) <- res(pr)/2
>
>
> # project the values of RasterLayer 'r' to the new RasterLayer 'projras'
> projras <- projectRaster(r0, pr)
>
> ## now go back to sp and extract matrix
>
> spprojras <- as(projras, "SpatialGridDataFrame")
>
> m <- as.image.SpatialGridDataFrame(spprojras)$z
>
> image(m)
>
>
> I'm not sure if the coercion to SpatialGridDataFrame will
> automatically give you all of the detail in the source by default for
> large grids, but there would be a way.
>
> Cheers, MIke.
> On Wed, Oct 27, 2010 at 7:03 PM,  <fsantos at ujaen.es> wrote:
>> Dear R community,
>>
>> I'm sorry, but I am newbie with GIS. I have to import a tiff using a
>> geotiff tool, and convert it into a data matrix. The initial projection is
>> Lambert Azimuthal Equal Area, and I would like to get the final matrix in
>> a regular lat/lon grid.
>>
>> It is possible to do it with R?
>>
>> Thanks in advance.
>>
>> _______________________________________________
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>>
>
>
>
> --
> Michael Sumner
> Institute for Marine and Antarctic Studies, University of Tasmania
> Hobart, Australia
> e-mail: mdsumner at gmail.com
>
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