[R-sig-Geo] ASCII grids as spatialgridframe

[ONKELINX, Thierry]

Hi Els,

You need to append only the data from the grid and not the grid itself.

Here is an example with the meuse dataset (available in sp).

data(meuse.grid)
m <- SpatialPixelsDataFrame(points = meuse.grid[c("x", "y")], data =
meuse.grid)
m2 <- SpatialPixelsDataFrame(points = meuse.grid[c("x", "y")], data =
data.frame(extra = sqrt(meuse.grid$dist)))

#this is what you tried.
m[["extra"]] <- m2 

#this is what you should do.
m$extra <- m2$extra

Best regards,

Thierry

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be

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than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
data.
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-----Oorspronkelijk bericht-----
Van: r-sig-geo-bounces at stat.math.ethz.ch
[mailto:r-sig-geo-bounces at stat.math.ethz.ch] Namens Els Ducheyne
Verzonden: donderdag 23 juli 2009 14:32
Aan: r-sig-geo at stat.math.ethz.ch
Onderwerp: [R-sig-Geo] ASCII grids as spatialgridframe

Dear all
sorry to post this question, but I have been looking across multiple
fora and haven't found the answer

I am trying to read ascii-grids in R using the shapefile -
read.asciigrid I have found that this is of class SpatialGridDataFrame I
would like to combine this with a set of grids that are already in the
workspace but when i use the [[<-option I always get the following error
What am I doing wrong? I am not using rgdal, because of a linking error
that I cannot seem to overcome - even though the installation of rgdal
and all its dependencies didn't yield an erro

Thanks for any help!

  achandata<-read.asciigrid("achan.asc")
 > summary(achandata)
Object of class SpatialGridDataFrame
Coordinates:
            min    max
coords.x1 -2.5 1002.5
coords.x2 -2.5  502.5
Is projected: NA
proj4string : [NA]
Number of points: 2
Grid attributes:
   cellcentre.offset cellsize cells.dim
1                 0        5       201
2                 0        5       101
Data attributes:
    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
  0.0000  0.0000  0.3000  0.7088  0.9000  6.2000  >
grids[["achan"]]<-achandata
Error: object is not subsettable
 > summary(grids)
Object of class SpatialGridDataFrame
Coordinates:
            min    max
coords.x1 -2.5 1002.5
coords.x2 -2.5  502.5
Is projected: NA
proj4string : [NA]
Number of points: 2
Grid attributes:
   cellcentre.offset cellsize cells.dim
1                 0        5       201
2                 0        5       101
Data attributes:
       elev            grad
  Min.   :119.8   Min.   :0.0008663
  1st Qu.:140.0   1st Qu.:0.0399718
  Median :144.0   Median :0.0620299
  Mean   :144.3   Mean   :0.0821328
  3rd Qu.:150.1   3rd Qu.:0.1129532
  Max.   :159.5   Max.   :0.3284767

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