melt spatialPixelDataFrame

Hi,

I tried:
1) to transform the SPDF to a normal dataframe with as.data.frame(spdf)

but then I loose my x and y columns. Thus I can't use them in melt. Was
that behavior changed recently?

No, I really don't think so. Are you sure?  Here x.1 and y.1 are the
(re-attached) grid point coordinates, which incidentally are copies of
the original data "x" and "y".

data(meuse.grid)
m = SpatialPixelsDataFrame(points = meuse.grid[c("x", "y")], data =
meuse.grid)
head(as.data.frame(m))
       x      y part.a part.b      dist soil ffreq    x.1    y.1
1 181180 333740      1      0 0.0000000    1     1 181180 333740
2 181140 333700      1      0 0.0000000    1     1 181140 333700
3 181180 333700      1      0 0.0122243    1     1 181180 333700

I am not 100% sure but my output looks different from yours (I am missing x.1 and y.1, the original coords from the SPDF and not the re-attached ones)
Here the output with the same example and sessionInfo():

library(raster)

Loading required package: sp
raster 2.0-08 (27-June-2012)

data(meuse.grid)
m = SpatialPixelsDataFrame(points = meuse.grid[c("x", "y")], data = meuse.grid)
head(as.data.frame(m))

x      y part.a part.b      dist soil ffreq
1 181180 333740      1      0 0.0000000    1     1
2 181140 333700      1      0 0.0000000    1     1
3 181180 333700      1      0 0.0122243    1     1
4 181220 333700      1      0 0.0434678    1     1
5 181100 333660      1      0 0.0000000    1     1
6 181140 333660      1      0 0.0122243    1     1

sessionInfo()

R version 2.14.1 (2011-12-22)
Platform: i686-pc-linux-gnu (32-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=C                 LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods  
[7] base     

other attached packages:
[1] raster_2.0-08 sp_0.9-99    

loaded via a namespace (and not attached):
[1] grid_2.14.1    lattice_0.20-0 tools_2.14.1 




Any idea?

/johannes