[STATSGRASS] unfilled matrices with R and gstat in grass 6.2.0beta3

[Edzer J. Pebesma]

Roger, we can't look over your shoulder. Please send the script you used 
to create the right (but odd) and the wrong results, as complete as 
possible.

Thanks,
--
Edzer

roger at spinn.net wrote:
>
> Folks,
> This is a user's question, rather than a developer's question.
> I have R with the gstat library working with grass6.2.0beta3.  On 
> Linux 2.6.13 x86_64 (SuSE 10.0).  The software generally works and I 
> can confirm its results at least approximately against other 
> software.  The problem I'm having is that the resulting map is 
> sometimes not completely filled.  I get calculated values on diagonal 
> lines in the map and the intervening areas are left unfilled -- they 
> have null values.  The same pattern is visible whether I look at the 
> result from within R or export the result to a grass raster file.
> The pattern is not so simple as a limit to the size of the resulting 
> map.  I have a small set of data (about 60 locations) and need to 
> construct a map of an area of about 20x30 km, using a grid with 
> spacing of 30mX30m.  The resulting map should have 686736 values, but 
> the the result only contains 171684 non-null values.  That is exactly 
> 1/4 of the cells.  If I increase the cell area to 60mX60m so that the 
> grid only contains 171684 cells, then the result contains 85842 
> non-null values.  That is 1/2 of the cells.
> I can construct a map using 16 tiles across the same area and patch 
> them together to get a completely filled map, but for most purposes 
> that is an excessive amount of work.
> With a different data set with about 250 points and trying to 
> construct a map over a larger area using a grid with 169576 cells, 
> each 120mX120m I do get a filled raster map in the result, though the 
> result looks a little odd.
> I don't understand what is happening and I've found no mention of this 
> problem elsewhere.  Any ideas?
>
> Roger Miller
>
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