[R-sig-Geo] aggregate() error on large files in raster

[Robert J. Hijmans]

Koen,
That's a bug. You can, indeed, avoid it by using expand=TRUE (perhaps
followed by crop to remove the expanded area). This will be fixed in
next version of raster.
Robert

On Mon, Jul 1, 2013 at 5:49 AM, Koen Hufkens <koen.hufkens at gmail.com> wrote:
> Hi everyone,
>
> I've been experiencing errors using the aggregate() raster function on
> large files. It only seems to happen when using the expand=FALSE option.
>
> The warning I get reads:
>
> Warning message:
> In .rasterFromRasterFile(grdfile, band = band, objecttype) :
>   size of values file does not match the number of cells (given the data
> type)
>
> And most of the time the bottom rows of the resulting aggregated image
> contains values that read -3.4e+38 (which to me is rather arbitrairy).
>
> I'm running:
> R version 3.0.1 (2013-05-16) -- "Good Sport"
> Platform: x86_64-pc-linux-gnu (64-bit)
> raster 2.1-37
>
> Any clues on how to solve this would be appreciated. The error also seems
> to be limited to large files > 5000 x 5000 pixels or so.
>
> Best,
> Koen
>
>
> --------------
> a copy of the example code:
>
>
>> # aggregate error on large files
>>
>> # read image
>> img <- mean(brick('/home/khufkens/virton.tif'))
>> # show image info
>> img
> class       : RasterLayer
> dimensions  : 10342, 10342, 106956964  (nrow, ncol, ncell)
> resolution  : 0.7464698, 0.7464698  (x, y)
> extent      : 611736.7, 619456.7, 6379237, 6386957  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0
> +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs
> data source :
> /tmp/R_raster_tmp/khufkens/raster_tmp_2013-07-01_142516_99728.grd
> names       : layer
> values      : 0, 213.3333  (min, max)
>
>> # set window size
>> windowsize <- 81
>
>> zones <- aggregate(img,fact=windowsize,fun=mean,expand=TRUE,na.rm=TRUE)
>> # show results info
>> zones
> class       : RasterLayer
> dimensions  : 128, 128, 16384  (nrow, ncol, ncell)
> resolution  : 60.46405, 60.46405  (x, y)
> extent      : 611736.7, 619476.1, 6379218, 6386957  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0
> +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs
> data source :
> /tmp/R_raster_tmp/khufkens/raster_tmp_2013-07-01_142555_110676.grd
> names       : layer
> values      : 24.63222, 138.7439  (min, max)
>
>> zones <- aggregate(img,fact=windowsize,fun=mean,expand=FALSE,na.rm=TRUE)
>> # BAM!
> Warning message:
> In .rasterFromRasterFile(grdfile, band = band, objecttype) :
>   size of values file does not match the number of cells (given the data
> type)
>
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>
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