# You could do this:

dem100 <- resample(dem, CODEQP, method='bilinear')


# But as the resolutions are rather different, I think it is better to first
aggregate such that they are about the same:

temp <- aggregate(dem, 10)

# And then use resample:

dem100 <- resample(temp, CODEQP, method='bilinear')


Robert


On Fri, Jul 15, 2011 at 5:09 AM, Barry Rowlingson <
b.rowlingson@lancaster.ac.uk> wrote:

> On Fri, Jul 15, 2011 at 11:10 AM, Agustin Lobo <alobolistas@gmail.com>
> wrote:
> > I have 2 raster objects
> >
> >> show(CODEQP)
> > class       : RasterLayer
> > dimensions  : 10, 10, 100  (nrow, ncol, ncell)
> > resolution  : 100, 100  (x, y)
> > extent      : 438048.4, 439048.4, 4633415, 4634415  (xmin, xmax, ymin,
> ymax)
> > coord. ref. : +proj=utm +zone=31 +ellps=intl +units=m +no_defs
> > values      : in memory
> > min value   : 1
> > max value   : 1
> >
> >> dem = raster("mde10mny.tif")
> >> show(dem)
> > class       : RasterLayer
> > dimensions  : 2333, 2788, 6504404  (nrow, ncol, ncell)
> > resolution  : 10, 10  (x, y)
> > extent      : 435926.9, 463806.9, 4613063, 4636393  (xmin, xmax, ymin,
> ymax)
> > coord. ref. : NA
> > values      : /media/Iomega_HDD/DIPU2011/RVISITANTS/mde10mny.tif
> > min         : ?
> > max         : ?
> >
> > and want to make a thrid object "dem100" perfectly aligned to CODEQP.
> >
> > I've tried with crop() but, as noted in the help page, the input
> > extent is actually modified to get aligned to the input
> > raster pixels and I actually would like the opposite:
> >
> >> dem100 = crop(dem,extent(CODEQP))
> >> show(dem100)
> > class       : RasterLayer
> > dimensions  : 100, 100, 10000  (nrow, ncol, ncell)
> > resolution  : 10, 10  (x, y)
> > extent      : 438046.9, 439046.9, 4633413, 4634413  (xmin, xmax, ymin,
> ymax)
> > coord. ref. : NA
> > values      : in memory
> > min value   : 549.4215
> > max value   : 627.9377
> >
> >> show(CODEQP)
> > class       : RasterLayer
> > dimensions  : 10, 10, 100  (nrow, ncol, ncell)
> > resolution  : 100, 100  (x, y)
> > extent      : 438048.4, 439048.4, 4633415, 4634415  (xmin, xmax, ymin,
> ymax)
> > coord. ref. : +proj=utm +zone=31 +ellps=intl +units=m +no_defs
> > values      : in memory
> > min value   : 1
> > max value   : 1
> >
> > Note they are not identical.
> >
> > Is there any way (besides using grass from within R) to get dem100 to
> > have the same geometry (extent and pixel size) than CODEQP?
>
>  I think that doing a crop() can only return cells that are directly
> taken from the input raster. Your CODEQP raster doesn't align to the
> dem raster, so what you want is not a crop but will involve some kind
> of interpolation, as your target extent cells overlap more than one
> input raster cells.
>
>  Possibly extract() will do it?
>
> Barry
>

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