Robert,
Thanks for the input.
Looks like resample() and terrain() return the same values, which is
reassuring.
G
On Mon, Sep 16, 2013 at 5:38 PM, Robert J. Hijmans <r.hijm...@gmail.com>wrote:
> Gabrielle you are right, if the resolution is in fact different -- I
> did not look carefully enough at the decimals -- then crop/extend
> won't work and you will need resample.
> Another approach would be to use the "terrain" function in raster and
> compute slope and aspect from the elevation data.
> Robert
>
> On Sun, Sep 15, 2013 at 11:50 PM, Gabriele Cozzi <gab.co...@gmail.com>
> wrote:
> > Dear Robert,
> >
> > thank you for going through my post again. Really appreciated
> >
> > I just tried what you suggested but neither crop() nor extend() do fix my
> > problem; the extent and the resolution of forest remains different from
> > slope and aspect
> >
> > Indeed aspect and slope have one more column than altitude, but I believe
> > this is the result of the resolution being different in the original
> rasters
> >
> > res(aspect)
> > res(slope)
> > # 27.28532 27.28532
> >
> > res(altitude)
> > # 27.28532 27.28677
> >
> > I believe this is the reason why cropping (or extending) does not work
> > because a raster cannot be cropped using an extent that does not allow
> for a
> > finite number of rows?
> > I think that cropping aspect with altitude would result in a decimal
> number
> > nrow(aspect) = xxx.y and a raster row can not take decimals?
> >
> > Does this make sense?
> >
> > Any further suggestion is appreciated
> >
> > I think I will also try to find out why, to begin with, the 3 raster
> layers
> > that I was given have different resolution. They all come from the same
> > satellite imagery so they should have the same resolution.
> >
> > Thanks in advance,
> >
> > Gabriele
> >
> >
> >
> > On Mon, Sep 16, 2013 at 8:07 AM, Robert J. Hijmans <r.hijm...@gmail.com>
> > wrote:
> >>
> >> Gabriele,
> >>
> >> That is not the best solution in this case; resampling should be a
> >> function of last resort. As Lionel pointed out, aspect has one more
> >> column than altitude, but has otherwise the same parameters.
> >> Therefore, the approach should be using the crop function (which you
> >> used, but after first making a mistake with res).
> >>
> >> asp = crop(aspect, altitude)
> >> slp = crop(slope, altitude)
> >>
> >> OR the opposite route; add the row to the altitude raster:
> >>
> >> alt = extend(altitude, aspect)
> >>
> >> Robert
> >>
> >> On Thu, Sep 12, 2013 at 8:45 AM, Gabriele Cozzi <gab.co...@gmail.com>
> >> wrote:
> >> > Lionel, Paco,
> >> >
> >> > thanks for the quick answers.
> >> >
> >> > Going through your suggestions I found that the function *resample
> >> > {raster}
> >> > *that transfers values between non matching Raster* objects (in terms
> of
> >> > origin and resolution) does exactly what I need.
> >> >
> >> > *resample* is actually embedded in the function *spatial_sync_raster*
> >> > that
> >> > I had problems to run. When I tried to run it I got the following
> error
> >> > message:
> >> >
> >> > Error in spatial_sync_raster(alt, slo, method = "ngb", verbose =
> FALSE)
> >> > :
> >> > could not find function "expand"
> >> >
> >> > *expand* is not part of the package climstats and I am not quite sure
> >> > where
> >> > to find it...
> >> >
> >> > But as said, *resample()* solved my problem.
> >> >
> >> > Thanks!
> >> >
> >> >
> >> > Gabriele
> >> >
> >> >
> >> >
> >> > On Thu, Sep 12, 2013 at 1:33 PM, Francisco Rodriguez Sanchez <
> >> > f.rodriguez.s...@gmail.com> wrote:
> >> >
> >> >> Hi Gabriele,
> >> >>
> >> >> Try the spatial_sync_raster function in package climstats:
> >> >>
> >> >> https://r-forge.r-project.org/**projects/climstats/<
> https://r-forge.r-project.org/projects/climstats/>.
> >> >> It will align the projection, extent and resolution of your rasters
> all
> >> >> at
> >> >> once
> >> >>
> >> >> Hope it helps,
> >> >>
> >> >> Paco
> >> >>
> >> >>
> >> >> El 12/09/2013 11:59, Gabriele Cozzi escribió:
> >> >>
> >> >> Dear list,
> >> >>>
> >> >>> I was given three raster files with 'slope', 'aspect' and 'altitude'
> >> >>> of my
> >> >>> study site. I realised that one of the three rasters (namely
> >> >>> 'altitude')
> >> >>> has a slightly different raster cell resolution, which results in a
> >> >>> slightly different raster extent and does not allow me to
> >> >>> raster::stack()
> >> >>> the three layers to create a single stack object.
> >> >>> I tried to change the raster resolution using raster::res() for the
> >> >>> raster
> >> >>> 'altitude' but, when I subsequently cropped the three rasters with
> an
> >> >>> object of class extent, I still got different extents between "slope
> >> >>> and
> >> >>> aspect" vs. "altitude".
> >> >>>
> >> >>> Any advice on how to solve this cell resolution incongruence is very
> >> >>> welcome.
> >> >>> Here below I report the output to make things more understandable.
> >> >>>
> >> >>> Thanks in advance,
> >> >>> Gabriele
> >> >>>
> >> >>>
> >> >>>
> >> >>> #----------------
> >> >>> #----------------
> >> >>>
> >> >>> aspect <- raster("~/Envir/aspect/prj.**adf")
> >> >>> slope <- raster("~/Envir/slope/prj.adf"**)
> >> >>> altitude <- raster("~/Envir/**20130508094222_992463356.tif")
> >> >>>
> >> >>> aspect ( N.B. 'slope' returns exactly the same attributes!)
> >> >>> #class : RasterLayer
> >> >>> #dimensions : 9813, 8428, 82703964 (nrow, ncol, ncell)
> >> >>> #resolution : 27.28532, 27.28532 (x, y)
> >> >>> #extent : 135446.9, 365407.6, 4345919, 4613669 (xmin,
> xmax,
> >> >>> ymin,
> >> >>> ymax)
> >> >>> #coord. ref. : +proj=utm +zone=38 +ellps=WGS84
> >> >>> +towgs84=0,0,0,0,0,0,0
> >> >>> +units=m +no_defs
> >> >>>
> >> >>> altitude
> >> >>> #class : RasterLayer
> >> >>> #dimensions : 9812, 8428, 82695536 (nrow, ncol, ncell)
> >> >>> #resolution : 27.28532, 27.28677 (x, y)
> >> >>> #extent : 135446.9, 365407.6, 4345919, 4613656 (xmin,
> xmax,
> >> >>> ymin,
> >> >>> ymax)
> >> >>> #coord. ref. : +proj=utm +zone=38 +datum=WGS84 +units=m +no_defs
> >> >>> +ellps=WGS84 +towgs84=0,0,0
> >> >>>
> >> >>> ex <- extent(animal_locations)
> >> >>> ex
> >> >>> #class : Extent
> >> >>> #xmin : 257473.1
> >> >>> #xmax : 312499.1
> >> >>> #ymin : 4452821
> >> >>> #ymax : 4570717
> >> >>>
> >> >>> Before using the function raster.crop <- crop('raster_file', ex) to
> >> >>> crop
> >> >>> all rasters to the same extent, I tried to change the resolution of
> >> >>> 'altitude' using
> >> >>>
> >> >>> res(altitude) <- 27.28532
> >> >>>
> >> >>> altitude
> >> >>> #class : RasterLayer
> >> >>> #dimensions : 9813, 8428, 82703964 (nrow, ncol, ncell)
> >> >>> #resolution : 27.28532, 27.28532 (x, y)
> >> >>> #extent : 135446.9, 365407.6, 4345905, 4613656 (xmin,
> xmax,
> >> >>> ymin,
> >> >>> ymax)
> >> >>> #coord. ref. : +proj=utm +zone=38 +datum=WGS84 +units=m +no_defs
> >> >>> +ellps=WGS84 +towgs84=0,0,0
> >> >>>
> >> >>> When I then run crop() for aspect and the new defined altitude I
> >> >>> however
> >> >>> become different extents (i.e. ymin and ymax) despite now the
> >> >>> dimensions
> >> >>> and resolutions are the same
> >> >>>
> >> >>> crop(aspect, ex)
> >> >>> #class : RasterLayer
> >> >>> #dimensions : 5054, 2749, 13893446 (nrow, ncol, ncell)
> >> >>> #resolution : 27.28532, 27.28532 (x, y)
> >> >>> #extent : 247480.5, 322487.8, 4442809, 4580709 (xmin,
> xmax,
> >> >>> ymin,
> >> >>> ymax)
> >> >>> #coord. ref. : +proj=utm +zone=38 +ellps=WGS84
> >> >>> +towgs84=0,0,0,0,0,0,0
> >> >>> +units=m +no_defs
> >> >>> #names : prj
> >> >>> #values : -1, 359.8158 (min, max)
> >> >>>
> >> >>> crop(altitude, ex)
> >> >>> #class : RasterLayer
> >> >>> #dimensions : 5054, 2749, 13893446 (nrow, ncol, ncell)
> >> >>> #resolution : 27.28532, 27.28532 (x, y)
> >> >>> #extent : 247480.5, 322487.8, 4442823, 4580723 (xmin,
> xmax,
> >> >>> ymin,
> >> >>> ymax)
> >> >>> #coord. ref. : +proj=utm +zone=38 +datum=WGS84 +units=m +no_defs
> >> >>> +ellps=WGS84 +towgs84=0,0,0
> >> >>>
> >> >>> It also appears to me that by redefining res(altitude) I loose the
> >> >>> actual
> >> >>> values assigned to each pixel. Is there an argument to assign to the
> >> >>> new
> >> >>> pixels the value of the centre of the pixel?
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >> --
> >> >> Dr Francisco Rodriguez-Sanchez
> >> >> Forest Ecology and Conservation Group
> >> >> Department of Plant Sciences
> >> >> University of Cambridge
> >> >> Downing Street
> >> >> Cambridge CB2 3EA
> >> >> United Kingdom
> >> >>
> >> >> http://sites.google.com/site/**rodriguezsanchezf<
> http://sites.google.com/site/rodriguezsanchezf>
> >> >>
> >> >>
> >> >> ______________________________**_________________
> >> >> R-sig-Geo mailing list
> >> >> R-sig-Geo@r-project.org
> >> >>
> >> >> https://stat.ethz.ch/mailman/**listinfo/r-sig-geo<
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo>
> >> >>
> >> >
> >> >
> >> >
> >> > --
> >> > Gabriele Cozzi
> >> > Postdoctoral Research Associate
> >> > Population Ecology Research Group
> >> > http://www.popecol.org
> >> >
> >> > Zurich University
> >> > Institute of Evolutionary Biology and Environmental Studies
> >> > Winterthurerstr. 190
> >> > 8057 Zurich - Switzerland
> >> > E-mail: gabriele.co...@uzh.ch
> >> > Phone: +41(0)44 635 49 12
> >> > Fax: +41(0)16355711
> >> > http://www.ieu.uzh.ch
> >> >
> >> > [[alternative HTML version deleted]]
> >> >
> >> >
> >> > _______________________________________________
> >> > R-sig-Geo mailing list
> >> > R-sig-Geo@r-project.org
> >> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >> >
> >
> >
> >
> >
> > --
> > Gabriele Cozzi
> > Postdoctoral Research Associate
> > Population Ecology Research Group
> > http://www.popecol.org
> >
> > Zurich University
> > Institute of Evolutionary Biology and Environmental Studies
> > Winterthurerstr. 190
> > 8057 Zurich - Switzerland
> > E-mail: gabriele.co...@uzh.ch
> > Phone: +41(0)44 635 49 12
> > Fax: +41(0)16355711
> > http://www.ieu.uzh.ch
> >
>
--
Gabriele Cozzi
Postdoctoral Research Associate
Population Ecology Research Group
http://www.popecol.org
Zurich University
Institute of Evolutionary Biology and Environmental Studies
Winterthurerstr. 190
8057 Zurich - Switzerland
E-mail: gabriele.co...@uzh.ch
Phone: +41(0)44 635 49 12
Fax: +41(0)16355711
http://www.ieu.uzh.ch
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