[R-sig-Geo] SpatialPoints to SpatialGridDataFrame problems

[Hailey Eckstrand]

Hello All,
I am trying to convert some points to a SpatialGridDataFrame and am running
into difficulties.
When I convert the SpatialPointsDataFrame into a gridded object, it gives
many warning messages
and the output is incorrect. It says that the cellsize is 500x500 which is
incorrect, it is actually 50,000 by 50,000)

my.pts <- SpatialPointsDataFrame(coords=spatial.coords, data=my.df,
proj4string=CRS(p4s))
 gridded(my.pts) <- T

Warning messages:
1: In points2grid(points, tolerance, round) :
  grid has empty column/rows in dimension 1
2: In points2grid(points, tolerance, round) :
  grid topology may be corrupt in dimension 1
3: In points2grid(points, tolerance, round) :
  grid has empty column/rows in dimension 2
4: In points2grid(points, tolerance, round) :
  grid topology may be corrupt in dimension 2

str(my.pts)
Formal class 'SpatialPixelsDataFrame' [package "sp"] with 7 slots
  ..@ data       :'data.frame': 35 obs. of  2 variables:
  .. ..$ X1: num [1:35] 140.5 84.2 66.3 74.7 98.2 ...
  .. ..$ X2: num [1:35] 155.8 73.9 57.4 72.6 88.4 ...
  ..@ coords.nrs : num(0)
  ..@ grid       :Formal class 'GridTopology' [package "sp"] with 3 slots
  .. .. ..@ cellcentre.offset: Named num [1:2] -633000 -4422000
  .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
  .. .. ..@ cellsize         : Named num [1:2] 500 500
  .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
  .. .. ..@ cells.dim        : Named int [1:2] 503 902
  .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
  ..@ grid.index : int [1:35] 453405 453505 453605 453706 402904 403005
403105 403205 403305 403406 ...
  ..@ coords     : num [1:35, 1:2] -532500 -482500 -432500 -382000 -633000
...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "x" "y"
  ..@ bbox       : num [1:2, 1:2] -633250 -4422250 -381750 -3971250
  .. ..- 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=stere +lat_0=90 +lat_ts=60 +lon_0=-110
+k=1 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs
+towgs84=0,0,0"


I have also tried to build the GridTopology & glue it together with my data:

gtop.coords.min <- c(min(spatial.coords[,1]), min(spatial.coords[,2]))
gtop.coords.max <- c(max(my.coords[,1]), max(my.coords[,2]))
gtop.cell.size <- c(50000, 50000)
gtop.cells.dim.xc <- length(seq(gtop.coords.min[1], gtop.coords.max[1],
by=gtop.cell.size[1]))
gtop.cells.dim.yc <- length(seq(gtop.coords.min[2], gtop.coords.max[2],
by=gtop.cell.size[2]))
 gtop.cells.dim <- c(gtop.cells.dim.xc, gtop.cells.dim.yc)
cangrid.gtop <- GridTopology(gtop.coords.min, gtop.cell.size,
gtop.cells.dim)
str(cangrid.gtop)
Formal class 'GridTopology' [package "sp"] with 3 slots
  ..@ cellcentre.offset: num [1:2] -633000 -4422000
  ..@ cellsize         : num [1:2] 50000 50000
  ..@ cells.dim        : int [1:2] 6 10

SpatialGridDataFrame(grid=cangrid.gtop, data=my.df, proj4string=CRS(p4s))
Error in validityMethod(object) :
  unequal number of objects in full grid and data slot


I have included an image of what the coordinates look like. Here is a
description of my variables:
p4s
"+proj=stere +lat_0=90 +lat_ts=60 +lon_0=-110 +k=1 +x_0=0 +y_0=0
+ellps=GRS80 +datum=NAD83 +units=m +no_defs"

spatial.coords
         x        y
1  -532500 -4422000
2  -482500 -4422000
3  -432500 -4422000
4  -382000 -4422000
5  -633000 -4372000
6  -582500 -4372000
7  -532500 -4372000
8  -482500 -4372000
9  -432500 -4372000
10 -382000 -4372000
11 -583000 -4322000
12 -532500 -4322000
13 -482500 -4322000
14 -432500 -4322000
15 -382000 -4322000
16 -583000 -4272000
17 -532500 -4272000
18 -482500 -4272000
19 -432500 -4272000
20 -382000 -4272000
21 -583000 -4222000
22 -532500 -4222000
23 -482500 -4222000
24 -432500 -4222000
25 -583000 -4172000
26 -532500 -4172000
27 -482500 -4172000
28 -583000 -4122000
29 -532500 -4122000
30 -482500 -4122000
31 -633000 -4071500
32 -583000 -4072000
33 -532500 -4072000
34 -583000 -4021500
35 -633000 -3971500

str(my.df)
'data.frame':   35 obs. of  2 variables:
 $ X1: num  140.5 84.2 66.3 74.7 98.2 ...
 $ X2: num  155.8 73.9 57.4 72.6 88.4 ...

Many thanks,
Hailey
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