how to go from SpatialGrid to SpatialGridDataFrame ?

Edzer,

the class is:

class(data.new_alb[gd.glm,])

[1] "SpatialPointsDataFrame"
attr(,"package")
[1] "sp"

class(data.grd)

[1] "SpatialGrid"
attr(,"package")
[1] "sp"

I use the [gd.glm,] to avoid the NA in the datasets for that   
variable. However, I get the same results when omitted

Error in krige(glmpred ~ 1, data = data.new_alb, newd = data.grd) :
    no direct or inherited method for function 'krige' for this call

this indicates that the problem is elsewhere.

If newdata accepts SpatialGrids will it output a  
SpatialGridDataFrame  with the prediction as a dataframe of that?

Regarding the example, I am not quite sure that I understand how  
to  adapt the example to my data. I have a generated a grid based  
on my  grass extend, and I need the predictions from my model (idw  
in this  'toy' example) to go in that grid. In the meuse.grid  
example, you  have a regular grid of samples and make a grid based  
on that, I have  irregular samples and need to create a continuous  
surface of those  values. So, I chose to build the GridTopology  
from my grass location.

thanks

Horacio



On Feb 1, 2006, at 12:54 PM, Edzer J. Pebesma wrote:

A Horacio Samaniego wrote:

I wonder how I should go from a SpatialGrid to a  
SpatialGridDataFrame.

Using for example the function SpatialGridDataFrame()

I have defined a grid using the functions from the sp, gstat and   
spgrass6 packages:

G<-gmeta6()
kk<-SpatialGrid(GridTopology(c(G$south,G$west),c(G$nsres,G 
$ewres),c (G$rows,G$cols)),alb.proj)

str(kk)

Formal class 'SpatialGrid' [package "sp"] with 5 slots
  ..@ grid       :Formal class 'GridTopology' [package "sp"] with  
3  slots
  .. .. ..@ cellcentre.offset: num [1:2] -1333373 -2356259
  .. .. ..@ cellsize         : num [1:2] 1000 1000
  .. .. ..@ cells.dim        : int [1:2] 2899 4615
  ..@ grid.index : int(0)
  ..@ coords     : num [1:2, 1:2] -1333373  1564162 -2356259  2257928
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
  ..@ bbox       : num [1:2, 1:2] -1333872 -2356759  1564662  2258428
  .. ..- 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=aea +lat_1=29.75 +lat_2=45.25   
+lat_0=37.5 +lon_0=-96 +x_0=0 +y_0=0 +no_defs +a=6378137   
+rf=298.257222101 +towgs84=0.000,0"| __truncated__

Now I try to interpolate on that grid, with no success:
interp.vals<-idw(var1~1,data,newdata=kk)
Error in idw(corrext ~ 1, data = data.new_alb[gd.glm, ], newdata  
=  data.grd) :
    no direct or inherited method for function 'idw' for this call

So, I guess that I need to have a 'SpatialGridDataFrame' instead  
of  just 'SpatialGrid' as the interpolation needs to be assigned  
to a  spatial location

newdata can be of class SpatialGrid; probably idw fails because
of the data argument. What is the class of data.new_alb[gd.glm,] ?

kk2<-as(kk,'SpatialGridDataFrame');
Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots
  ..@ data       :Formal class 'AttributeList' [package "sp"]  
with  1 slots
  .. .. ..@ att: list()
  ..@ grid       :Formal class 'GridTopology' [package "sp"] with  
3  slots
  .. .. ..@ cellcentre.offset: num [1:2] -1333373 -2356259
  .. .. ..@ cellsize         : num [1:2] 1000 1000
  .. .. ..@ cells.dim        : int [1:2] 2899 4615
  ..@ grid.index : int(0)
  ..@ coords     : num [1:2, 1:2] -1333373  1564162 -2356259  2257928
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
  ..@ bbox       : num [1:2, 1:2] -1333872 -2356759  1564662  2258428
  .. ..- 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=aea +lat_1=29.75 +lat_2=45.25   
+lat_0=37.5 +lon_0=-96 +x_0=0 +y_0=0 +no_defs +a=6378137   
+rf=298.257222101 +towgs84=0.000,0"| __truncated__

promotes the grid to the correct class SpatialGridDataFrame but  
do  not assign to space for the variable. Is there any way to  
assign an  empty "slot" just as we would do for a data.frame?

To sum.  I cant seem to be able to create a "slot" (or z  
dimension)  to hold the output of my interpolation. Is there any  
trick out  there that I am missing? Any help will be appreciated.

thanks,

H