On Tue, 11 May 2010, manuel.schnei...@art.admin.ch wrote:
Dear list
I am trying to use SAGA function Vectorizing grid classes from R but
this creates an unclosed ring in the resulting shapefile. All steps work
in SAGA GUI. Maybe somebody can reproduce the error and help on it.
Otherwise, is there a direct way (in the sp framework) to convert grid
classes into polygons?
d <- SpatialGridDataFrame(GridTopology(c(0,0), c(1,1), c(5,6)),
data=data.frame(x=sample(rep(c(NA,1,2),10),30)))
write.asciigrid(d, "test.asc" , na.value=-9999)
rsaga.esri.to.sgrd(in.grids="test.asc", out.sgrd="classes.sgrd")
SAGA CMD 2.0.3
library path: C:/ManuProgs/R/R-2.10.1/library/RSAGA/saga_vc/modules
library name: io_grid
module name : Import ESRI Arc/Info Grid
author : (c) 2007 by O.Conrad
Parameters
Grid: [not set]
File: test.asc
ready
Save grid: classes.sgrd...
ready
rsaga.geoprocessor(lib="shapes_grid", module=6,
param=list(GRID="classes.sgrd", SHAPES="classes.shp", CLASS_ALL=1))
SAGA CMD 2.0.3
library path: C:/ManuProgs/R/R-2.10.1/library/RSAGA/saga_vc/modules
library name: shapes_grid
module name : Vectorising Grid Classes
author : (c) 2008 by O.Conrad
Load grid: classes.sgrd...
ready
Parameters
Grid system: 1; 5x 6y; 0x 0y
Grid: classes.sgrd
Shapes: Shapes
Class Selection: all classes
Class Identifier: 1.000000
Vectorised class as...: each island as separated polygon
vectorising class 1: 1.000000
vectorising class 2: 2.000000
Save shapes: classes.shp...
Save shapes: classes.shp
ready
Save table: classes.dbf...
ready
classes <- readOGR("classes.shp","classes")
OGR data source with driver: ESRI Shapefile
Source: "classes.shp", layer: "classes"
with 8 features and 3 fields
Feature type: wkbPolygon with 2 dimensions
Error in is.vector(X) : ring not closed
http://shapelib.maptools.org/dl/shapefile.pdf
does specify that a polygon in a shapefile must be closed. You may be able
to use readShapePoly(..., force_ring=TRUE) in maptools to work around the
problem.
Roger
Thanks in advance
Manuel
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--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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