[R-sig-Geo] HELP with RPyGeo and RSAGA slope function

[Alexander Brenning]

Dear Gianni,

ArcGIS is not that flexible; it does not allow you to directly create an 
ASCII raster as an output of a geoprocessing tool. Try this to create an 
ESRI raster "SLOPE" and then convert the result to ASCII:

setwd("C:/work")
env = rpygeo.build.env(overwriteoutput = 1,
            workspace = getwd())
rpygeo.geoprocessor(fun = "ASCIIToRaster_conversion",
      args = list("DEM.asc","DEM"), env=env)
rpygeo.Slope.sa("DEM","SLOPE",unit="PERCENT_RISE", env=env)
rpygeo.geoprocessor(fun = "RasterToASCII_conversion",
      args = list("SLOPE","SLOPE.asc"), env=env)
rpygeo.Delete.management("DEM", env=env)
rpygeo.Delete.management("SLOPE", env=env)


Regarding the (much faster) RSAGA solution, try this:

setwd("C:/work")
rsaga.esri.to.sgrd("DEM")
rsaga.slope("DEM","SLOPErad")
# convert to slope in percent:
rsaga.grid.calculus("SLOPErad","SLOPE", formula="100*tan(a)")
rsaga.sgrd.to.esri("SLOPE", prec = 4)
unlink(c("SLOPErad.*", "SLOPE.?grd", "SLOPE.sdat",
            "DEM.?grd", "DEM.sdat"))

I hope this helps...

cheers
  Alex


P.S.: You could also you the following call for converting ESRI raster 
to ASCII...

rpygeo.RasterToASCII.conversion("C:/work/SLOPE","C:/work/SLOPE.asc")

using the following function that is included in the next release of 
RPyGeo (to be available in the next days):

rpygeo.RasterToASCII.conversion = function(in.raster,
	out.ascii.file, ...)
{
     out.ascii.file = default.file.extension(out.ascii.file, ".asc")
     if (!(tolower(get.file.extension(out.ascii.file)) %in% c(".asc",
         ".txt")))
         stop("'out.ascii.file' must have extension '.asc' or '.txt'.\n")
     args = list(in.raster, out.ascii.file)
     rpygeo.geoprocessor(fun = "RasterToASCII_conversion", args = args,
         ...)
}





gianni lavaredo wrote:
> Hi All,
> 
> I am using Alexander Brenning RPyGeo. I have a DEM.asc (ASCII File format)
> and I wish to obtaion SLOPE (possible always in ascii formta) in percent.
> But I have this problem:
> 
>  rpygeo.Slope.sa("C:/work/DEM.asc","C:/work/SLOPE.asc",unit=c("PERCENT_RISE"),
> z.factor = 1)
> [1] "Executing: Slope C:/work/DEM.asc C:\\work\\SLOPE.asc PERCENT_RISE
> 1"
> [2] "Start Time: Mon Mar 02 19:03:30
> 2009"
> [3] "Failed to execute. Parameters are not
> valid."
> [4] "Parameter : C:\\work\\SLOPE.asc's extension is invalid for the output
> raster format."
> [5] "Failed to execute
> (Slope)."
> [6] "End Time: Mon Mar 02 19:03:30 2009 (Elapsed Time: 0.00
> seconds)"
> 
> I tryed several solutions but nothing. I tryed also with RSAGA but I don't
> understand the right code to have in "percent".
> 
> 
> Thanks
> 
> Gianni.
> 
> PS: for Prof. Alexander Brenning. this geoprocessing expression runs in
> RpyGEO
> 
> rpygeo.geoprocessing("Intersect_analysis"
> c("C:/work/plots.shp;C:/work/sample.shp", "C:/work/right_sample.shp",
> "ALL"))
> but I need to load the datas from the work folder
> 
> 	[[alternative HTML version deleted]]
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 
> 

-- 
Alexander Brenning
brenning at uwaterloo.ca - T +1-519-888-4567 ext 35783
Department of Geography and Environmental Management
University of Waterloo
200 University Ave. W - Waterloo, ON - Canada N2L 3G1
http://www.fes.uwaterloo.ca/geography/faculty/brenning/