spgrass6 (version 0.5-2)

readRAST6: Read and write GRASS 6 raster files

Description

Read GRASS 6 raster files from GRASS 6 into R SpatialGridDataFrame objects, and write single columns of R SpatialGridDataFrame objects to GRASS 6. readRAST6 and writeRAST6 use temporary binary files and r.out.bin and r.in.bin rather than the temporary ASCII files used in earlier implementations. The earlier versions may still be used in a transition period.

Usage

readRAST6(vname, cat=NULL, ignore.stderr = FALSE, NODATA=NULL)
writeRAST6(x, vname, zcol = 1, NODATA=NULL, ignore.stderr = FALSE)

Arguments

vname

A vector of GRASS 6.0 raster file names

cat

default NULL; if not NULL, must be a logical vector matching vname, stating which (CELL) rasters to return as factor

ignore.stderr

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

x

A SpatialGridDataFrame object for export to GRASS as a raster layer

zcol

Attribute column number or name

NODATA

by default NULL, in which case it is set to one less than floor()of the data values, otherwise an integer NODATA value (required to be integer by GRASS r.out.bin)

Value

• readRAST6 returns a SpatialGridDataFrame objects with an data.frame in the data slots, and with the projection argument set. Note that the projection argument set is the the GRASS rendering of proj4, and will differ from the WKT/ESRI rendering returned by readVECT6 in form but not meaning. They are exchangeable but not textually identical, usually with the +ellps= term replaced by ellipsoid parameters verbatim.

Examples

if (nchar(Sys.getenv("GISRC")) > 0) {
  spear <- readRAST6(c("geology", "elevation.dem"), cat=c(TRUE, FALSE),
    ignore.stderr=TRUE)
  table(spear$geology)
  if (Sys.getenv("OSTYPE") == "msys")
    Gver <- system("g.version.exe", intern=TRUE)
  else Gver <- system("g.version", intern=TRUE)
  if (Gver > "GRASS 6.2") {
    if (Sys.getenv("OSTYPE") == "msys") system("r.stats.exe --q -cl geology")
    else system("r.stats --q -cl geology")
  } else {
    if (Sys.getenv("OSTYPE") == "msys") system("r.stats.exe -q -cl geology")
    else system("r.stats -q -cl geology")
  }
  boxplot(spear$elevation.dem ~ spear$geology)
  spear$sqdem <- sqrt(spear$elevation.dem)
  writeRAST6(spear, "sqdemSP", zcol="sqdem", ignore.stderr=TRUE)
  if (Sys.getenv("OSTYPE") == "msys")
    system("r.info.exe sqdemSP", ignore.stderr=TRUE)
  else system("r.info sqdemSP", ignore.stderr=TRUE)
  if (Sys.getenv("OSTYPE") == "msys") system("g.remove.exe rast=sqdemSP")
  else system("g.remove rast=sqdemSP")
  if (Sys.getenv("OSTYPE") == "msys")
    system("r.mapcalc.exe quads0 = quads - 1", ignore.stderr=TRUE)
  else system("r.mapcalc 'quads0 = quads - 1'", ignore.stderr=TRUE)
  if (Sys.getenv("OSTYPE") == "msys")
    system("r.stats.exe -c quads0", ignore.stderr=TRUE)
  else system("r.stats -c quads0", ignore.stderr=TRUE)
  quads0 <- readRAST6("quads0", ignore.stderr=TRUE)
  table(quads0$quads0)
  quads0 <- readRAST6("quads0", ignore.stderr=TRUE)
  table(quads0$quads0)
  if (Sys.getenv("OSTYPE") == "msys") system("g.remove.exe rast=quads0")
  else system("g.remove rast=quads0")
}