Etienne,

Maybe you could give it a try with raster library as it is can read from
disc instead of loading in memory the whole image.

library(raster)
r2=raster("img/TM.burnpix.pnsc.2000-2006.freq.tif")
plot(r2)

Etienne (B. Racine)


On Mon, Mar 28, 2011 at 9:47 PM, Etienne <etiennesky@yahoo.com> wrote:

> Greetings,
>
> I am trying to plot a large raster dataset (2159x925 = 2M pixels) using
> spplot() and it fails with the following error after about 30 seconds:
>
> > r2=readGDAL("img/TM.burnpix.pnsc.2000-2006.freq.tif")
> > image(r2)
> > spplot(r2)
> Error: segfault from C stack overflow
>
> I can plot the same data fine with the image() function in less than a
> second.
>
> The main problem comes from the fact that many pixels are NA's (I do not
> wish to include some in the analysis).  If I set the NAs to zero, I can plot
> the data but it takes a very long time (about 30 seconds), using 100% cpu
> and a lot of memory (1GB) - orders of magnitude higher than using the
> image() function.
>
> Questions:
>
> 1)
> Is this volume of data supported by the spplot() function, and if so is
> there any trick to get this working properly and faster?
>
> 2)
> Can I work with NAs or must I convert them to another value (0,Nan ?)
>
> Many thanks,
> Etienne
>
> The dataset has the following structure,:
> =====
> > str(r2)
> Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots
>  ..@ data       :'data.frame': 1997075 obs. of  1 variable:
>  .. ..$ band1: num [1:1997075] NA NA NA NA NA NA NA NA NA NA ...
>  ..@ grid       :Formal class 'GridTopology' [package "sp"] with 3 slots
>  .. .. ..@ cellcentre.offset: Named num [1:2] 290965 7751395
>  .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
>  .. .. ..@ cellsize         : num [1:2] 30 30
>  .. .. ..@ cells.dim        : int [1:2] 2159 925
>  ..@ grid.index : int(0)
>  ..@ coords     : num [1:2, 1:2] 290965 355704 7751395 7779115
>  .. ..- attr(*, "dimnames")=List of 2
>  .. .. ..$ : NULL
>  .. .. ..$ : chr [1:2] "x" "y"
>  ..@ bbox       : num [1:2, 1:2] 290950 7751380 355719 7779130
>  .. ..- attr(*, "dimnames")=List of 2
>  .. .. ..$ : chr [1:2] "x" "y"
>  .. .. ..$ : chr [1:2] "min" "max"
>  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
>  .. .. ..@ projargs: chr " +proj=utm +zone=23 +south +ellps=WGS84
> +datum=WGS84 +units=m +no_defs +towgs84=0,0,0"
> =====
>
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