[GRASS-stats] another gstat error

[Jarek Jasiewicz]

Roger Bivand pisze:
> On Fri, 19 Jun 2009, Jarosław Jasiewicz wrote:
>
>> Hi
>> Another gstat error:
>>
>> var.krigged=krige(z~x+y,gr,grid,model=var.fitted)
>> [using universal kriging]
>>
>> "chfactor.c", line 130: singular matrix in function LDLfactor()
>> Error in predict.gstat(g, newdata = newdata, block = block, nsim = 
>> nsim,  :
>> LDLfactor
>
> Jarek:
>
> Shall I repeat what I wrote this morning? 
????
> Did you actually try omitting the x+y in the formula? 
Yes, before I send post I tried firrst z~(x+y)^2 and if it failed I used 
z~1 to try without drift. The same error ocurs
> Including a drift in untransformed coordinates is very likely to lead 
> to numerical chaos. If z~1 works, then the smoking gun is the x+y, 
> isn't it? If you want them, transform them (offset with for example 
> elide() in maptools and transform back afterwards).
>
> Roger
>
>>
>> I can't imagine the reason
>>
>> regards
>> Jarek
>>
>> here is structure of my gr spatialPointsDataFrame used in analysis:
>>
>> str(gr)
>> Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
>> ..@ data       :'data.frame':    2201 obs. of  5 variables:
>> .. ..$ cat: num [1:2201] 2 3 4 5 6 7 8 9 10 11 ...
>> .. ..$ naz: Factor w/ 874 levels "1000","1001",..: 874 1 2 3 4 5 6 7 
>> 8 9 ...
>> .. ..$ x  : num [1:2201] 360175 360176 360178 360169 360167 ...
>> .. ..$ y  : num [1:2201] 512736 512736 512733 512719 512712 ...
>> .. ..$ z  : num [1:2201] 86.5 87.4 87.7 86.9 86 ...
>> ..@ coords.nrs : num(0)
>> ..@ coords     : num [1:2201, 1:2] 360175 360176 360178 360169 360167 
>> ...
>> .. ..- attr(*, "dimnames")=List of 2
>> .. .. ..$ : NULL
>> .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
>> ..@ bbox       : num [1:2, 1:2] 359907 512481 360492 512778
>> .. ..- attr(*, "dimnames")=List of 2
>> .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
>> .. .. ..$ : chr [1:2] "min" "max"
>> ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
>> .. .. ..@ projargs: chr " +proj=tmerc +lat_0=0 +lon_0=19 +k=0.9993 
>> +x_0=500000 +y_0=-5300000 +no_defs +a=6378137 +rf=298.257222101 
>> +towgs84=0.000,0.000,"| __truncated__
>>
>> and newdata grid:
>> str(grid)
>> Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots
>> ..@ data       :'data.frame':    131352 obs. of  1 variable:
>> .. ..$ region2: int [1:131352] 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] 359902 512478
>> .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
>> .. .. ..@ cellsize         : num [1:2] 1.001 0.998
>> .. .. ..@ cells.dim        : int [1:2] 421 312
>> ..@ grid.index : int(0)
>> ..@ coords     : num [1:2, 1:2] 359902 360322 512478 512788
>> .. ..- attr(*, "dimnames")=List of 2
>> .. .. ..$ : NULL
>> .. .. ..$ : chr [1:2] "x" "y"
>> ..@ bbox       : num [1:2, 1:2] 359901 512477 360323 512789
>> .. ..- 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=tmerc +lat_0=0 +lon_0=19 +k=0.9993 
>> +x_0=500000 +y_0=-5300000 +no_defs +a=6378137 +rf=298.257222101 
>> +towgs84=0.000,0.000,"| __truncated__
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>