spgrass6 (version 0.5-2)

readVECT6: Read and write GRASS 6 vector object files

Description

readVECT6 moves one GRASS 6.0 vector object file with attribute data through a temporary shapefile to a Spatial*DataFrame object of type determined by the GRASS 6.0 vector object; writeVECT6 moves a Spatial*DataFrame object through a temporary shapefile to a GRASS vector object file. vect2neigh returns neighbour pairs with shared boundary length as described by Markus Neteler, in https://stat.ethz.ch/pipermail/r-sig-geo/2005-October/000616.html.

Usage

readVECT6(vname, type=NULL, remove.duplicates = TRUE, ignore.stderr = FALSE, with_prj=TRUE, with_c=FALSE)
writeVECT6(SDF, vname,  v.in.ogr_flags="", ignore.stderr = FALSE)
vInfo(vname, ignore.stderr = FALSE)
vColumns(vname, ignore.stderr = TRUE)
vDataCount(vname, ignore.stderr = TRUE)
vect2neigh(vname, ID=NULL, ignore.stderr = FALSE)
putSites6sp(SPDF, vname,  ignore.stderr = FALSE) 
putSites6(df, vname, ignore.stderr = FALSE)
getSites6sp(vname, ignore.stderr = FALSE, with_prj=TRUE) 
getSites6(vname, ignore.stderr = FALSE, with_prj=TRUE)

Arguments

vname

A GRASS 6.0 vector file name

type

override type detection when multiple types are non-zero, passed to v.out.ogr

remove.duplicates

In line and area vector objects, multiple geometrical features may be associated with a single cat number, leading to duplication of data rows; this argument attempts to combine the geometrical features so that they match a single data row

ignore.stderr

default FALSE, can be set to TRUE to silence system output to standard error; does not apply on Windows platforms

with_prj

default TRUE, write ESRI-style PRJ file for transfered data

with_c

if TRUE, export features with category (labeled) only; by default all features are exported

SDF

A Spatial*DataFrame to be moved to GRASS6 as a vector object, for SpatialPointsDataFrame, SpatialLinesDataFrame, and SpatialPolygonsDataFrame objects

v.in.ogr_flags

String containing additional optional flags and/or options for v.in.ogr, particularly -o and --overwrite

ID

A valid DB column name for unique identifiers (optional)

SPDF

A SpatialPointsDataFrame to be moved to GRASS6 as vector points

df

A data frame with at least columns named x, y and cat (no z support yet)

Value

• readVECT6 imports a GRASS6 vector object into a Spatial*DataFrame object with the type determined by the type of the GRASS6 vector object; getSites6 returns a data frame. vect2neigh returns a data frame object with left and right neighbours and boundary lengths, also given class GRASSneigh and spatial.neighbour (as used in spdep). The incantation to retrieve the neighbours list is sn2listw(vect2neigh())$neighbours, and to retrieve the boundary lengths: sn2listw(vect2neigh())$weights. The GRASSneigh object has two other useful attributes: external is a vector giving the length of shared boundary between each polygon and the external area, and total giving each polygon's total boundary length.

Examples

if (nchar(Sys.getenv("GISRC")) > 0) {
  if (Sys.getenv("OSTYPE") == "msys") system("v.info.exe bugsites")
  else system("v.info bugsites")
  vInfo("bugsites", ignore.stderr=TRUE)
  bugs <- readVECT6("bugsites", ignore.stderr=TRUE)
  summary(bugs)
  writeVECT6(bugs, "newbugs", v.in.ogr_flags="-o --overwrite", ignore.stderr=TRUE)
  if (Sys.getenv("OSTYPE") == "msys") system("v.info.exe newbugs")
  else system("v.info newbugs")
  vInfo("streams", ignore.stderr=TRUE)
  streams <- readVECT6("streams", type="line,boundary", remove.duplicates=FALSE, ignore.stderr=TRUE)
  summary(streams)
}