[R-sig-Geo] trouble coercing SpatialPixelsDataFrame into SpatialGridDataFrame?

[Roger Bivand]

On Wed, 20 Oct 2010, ElenaC wrote:

>
> I can't reproduce the problem with the meuse data either, so I've uploaded my
> original data:
> http://r-sig-geo.2731867.n2.nabble.com/file/n5655660/data_error.RData
> data_error.RData
>
> I get the problem when I do:
>
> library(sp)
> load("data_error.RData")
> summary(data_pixels)
> summary(as(data_pixels,'SpatialGridDataFrame'))

Thanks for posting the data. The problem is that your TRUE values are 
duplicate observations, so that TRUE is assigned to the grid cell first, 
because they come "before" FALSE (observations 1:241):

length(slot(data_pixels, "grid.index"))
length(unique(slot(data_pixels, "grid.index")))
zerodist(data_pixels)

How was the data_pixels object constructed? Did you intend to have 
duplicate pixels?

Maybe the SpatialPixels constructor should warn if points are duplicated?

Hope this helps,

Roger

>
>
> Here is the output from sessionInfo:
>
>> sessionInfo()
> R version 2.10.1 (2009-12-14)
> x86_64-apple-darwin9.8.0
>
> locale:
> [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] sp_0.9-65
>
> loaded via a namespace (and not attached):
> [1] grid_2.10.1    lattice_0.18-3
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no