Saving a spatial point object into a shapefile

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Hey,

The writeOGR function specifies (?writeOGR)
|obj| a SpatialPointsDataFrame, SpatialLinesDataFrame, or a 
SpatialPolygonsDataFrame object.

You need to convert first your SpatialPoints into spgdf

Best regards

Alex
Dear list members,

I am trying to save a spatial point object as a shapefile, but I got an
error that I do not have the right object class, why?

  >  sitiosMikeCRTM05
SpatialPoints:
               x       y
   [1,] 480244.6 1181636
   [2,] 480651.1 1184371
   [3,] 477555.2 1181189
   [4,] 486482.8 1167946
   [5,] 483764.4 1164624
   [6,] 477301.6 1192979
   [7,] 483737.4 1192048
   [8,] 480760.2 1192652
   [9,] 479985.8 1150756
[10,] 481748.5 1148902
[11,] 476126.6 1165617
[12,] 464735.7 1167079
[13,] 481182.4 1185941
[14,] 500632.8 1132727
Coordinate Reference System (CRS) arguments: +proj=tmerc +lon_0=-84
+lat_0=0 +x_0=500000 +k=0.9999 +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0

  >  writeOGR(sitiosMikeCRTM05,
dsn="C:/ProyectosRespacial/CBSS/Shapefiles_proyectados",
layer="sitiosMikeCRTM05", driver="ESRI Shapefile")
Error en writeOGR(sitiosMikeCRTM05, dsn =
"C:/ProyectosRespacial/CBSS/Shapefiles_proyectados",  :
    obj of wrong class

Best,

Manuel

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Alexandre Villers, PhD.
Postdoc researcher
Spatial Ecology & Population Dynamics
Section of Ecology, Department of Biology
University of Turku
FIN-20014 Turku
Finland

@mail: alexandre.villers at utu.fi
phone: 00358 (0)2 333 5049

Skype You can skype me (but think of using Ekiga instead !) 
<skype:aquila06?call>

*Use open source and free softwares*
<http://cran.r-project.org/> <http://grass.itc.it/> 
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Dear list members,

I am trying to save a spatial point object as a shapefile, but I got an 
error that I do not have the right object class, why?
Because the documentation sais so. ?writeOGR tells me:

Usage:

     writeOGR(obj, dsn, layer, driver, dataset_options = NULL,
layer_options=NULL, verbose = FALSE)

Arguments:

     obj: a SpatialPointsDataFrame, SpatialLinesDataFrame, or a
          SpatialPolygonsDataFrame object.
...

you can create a SpatialPointsDataFrame with dummy attributes from your
object by:

x = SpatialPointsDataFrame(sitiosMikeCRTM05, data.frame(dummy = rep(1,14))

 > sitiosMikeCRTM05
SpatialPoints:
              x       y
  [1,] 480244.6 1181636
  [2,] 480651.1 1184371
  [3,] 477555.2 1181189
  [4,] 486482.8 1167946
  [5,] 483764.4 1164624
  [6,] 477301.6 1192979
  [7,] 483737.4 1192048
  [8,] 480760.2 1192652
  [9,] 479985.8 1150756
[10,] 481748.5 1148902
[11,] 476126.6 1165617
[12,] 464735.7 1167079
[13,] 481182.4 1185941
[14,] 500632.8 1132727
Coordinate Reference System (CRS) arguments: +proj=tmerc +lon_0=-84 
+lat_0=0 +x_0=500000 +k=0.9999 +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0

 > writeOGR(sitiosMikeCRTM05, 
dsn="C:/ProyectosRespacial/CBSS/Shapefiles_proyectados", 
layer="sitiosMikeCRTM05", driver="ESRI Shapefile")
Error en writeOGR(sitiosMikeCRTM05, dsn = 
"C:/ProyectosRespacial/CBSS/Shapefiles_proyectados",  :
   obj of wrong class

Best,

Manuel

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster
Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics      e.pebesma at wwu.de
On Thu, Nov 4, 2010 at 10:25 AM, Edzer Pebesma

Because the documentation sais so. ?writeOGR tells me:

Usage:

? ? writeOGR(obj, dsn, layer, driver, dataset_options = NULL,
layer_options=NULL, verbose = FALSE)

Arguments:

? ? obj: a SpatialPointsDataFrame, SpatialLinesDataFrame, or a
? ? ? ? ?SpatialPolygonsDataFrame object.
Although that's not what the code says:

 if (!"data" %in% names(getSlots(class(obj))))
        stop("obj of wrong class")

 - it just looks to see if there's a 'data' slot in the argument, and
then carries on, stumbling blindly into all sorts of problems if one
is dumb enough to create a class with a data slot:

 > setClass("foo",representation(data="numeric"))
 > z=new("foo")
 > writeOGR(z,dsn="/tmp",layer="pts",driver="ESRI Shapefile")
Error in writeOGR(z, dsn = "/tmp", layer = "pts", driver = "ESRI Shapefile") :
  NULL NULL unknown data type

Surely there should be _methods_ for writeOGR for classes that it
supports, such as SpatialPointsDataFrame. Explicitly testing for the
presence of a slot/member is worse than explicitly testing for the
name of a class when you should really use 'inherits' which is worse
than the correct approach which is writing methods...

 *end mini-rant* :)

Barry
On Thu, Nov 4, 2010 at 10:25 AM, Edzer Pebesma
<edzer.pebesma at uni-muenster.de> wrote:

Because the documentation sais so. ?writeOGR tells me:

Usage:

    writeOGR(obj, dsn, layer, driver, dataset_options = NULL,
layer_options=NULL, verbose = FALSE)

Arguments:

    obj: a SpatialPointsDataFrame, SpatialLinesDataFrame, or a
         SpatialPolygonsDataFrame object.
Although that's not what the code says:

 if (!"data" %in% names(getSlots(class(obj))))
        stop("obj of wrong class")

 - it just looks to see if there's a 'data' slot in the argument, and
then carries on, stumbling blindly into all sorts of problems if one
is dumb enough to create a class with a data slot:

 > setClass("foo",representation(data="numeric"))
 > z=new("foo")
 > writeOGR(z,dsn="/tmp",layer="pts",driver="ESRI Shapefile")
Error in writeOGR(z, dsn = "/tmp", layer = "pts", driver = "ESRI Shapefile") :
  NULL NULL unknown data type

Surely there should be _methods_ for writeOGR for classes that it
supports, such as SpatialPointsDataFrame. Explicitly testing for the
presence of a slot/member is worse than explicitly testing for the
name of a class when you should really use 'inherits' which is worse
than the correct approach which is writing methods...

 *end mini-rant* :)
Although you're the first one to bring up this feature (bug?) of
writeOGR, I fully agree. Using methods would also allow e.g. package
raster to define a writeGDAL method for Raster, stacks, bricks, and the
like. In that case we might have to define the method first in sp (rgdal
depends on sp), so that other package don't require rgdal - CRAN still
does not provide OS-X and solaris ports.
Barry

Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster
Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics      e.pebesma at wwu.de