[R-sig-Geo] RSAGA multi.focal.function

[Alexander Brenning]

Hi,

the problem Nathan described has been solved, and a new release of RSAGA 
(0.9-7) is now available on CRAN.

The problem concerned the situation where radius >= 1 grid cells AND 
more than one input grid was used, i.e. most practical situations were 
not affected by this bug (e.g. applying a 'predict' method to a stack of 
input grids on a pixel-by-pixel basis was not affected because in this 
situation, radius = 0).

Thanks again Nathan for your input.

Best,
   Alex



On 27/05/2010 4:34 PM, Nathan Odgers wrote:
> Hi,
>
> I have been trying to get the RSAGA multi.focal.function function to
> work in R. This is how I have been calling it:
>
> multi.focal.function(in.grids=filestack,out.grid.prefix="test_multi",path="z:/saga/stack",
>
>
fun=returnfirstline,in.varnames=c("elev_v","fix_v"),radius=3,search.mode="square",mw.to.vector=FALSE,mw.na.rm=FALSE)
>
> where filestack is a vector containing the names of two grids: a DEM
> and another grid with integer values. The returnfirstline function
> prints (to the console) the arrays that multi.focal.function sends to
> returnfirstline. This is all very basic because for now I’m just
> trying to get a feel for how multi.focal.function works with multiple
> grids before I try and write a more complex function to use with it.
>
> In any case, this is the problem that I am having with it: everything
> seems to work in that returnfirstline prints the rectangular windows
> to the console output, but the problem is that multi.focal.function
> seems to set the first row of the input grids to NA values. This is
> what the header and first portion of the first four rows of the ascii
> DEM look like:
>
> ncols         202 nrows         202 xllcorner     -50010.3411746
> yllcorner     426994.8486065 cellsize      24.7883519 NODATA_value
> -9999 455 455 456 456 457 457 456 455 456 (…) 454 455 456 456 458 458
> 458 457 457 (…) 454 455 456 457 458 458 459 458 457 (…) 454 454 456
> 457 458 458 459 458 457 (…)
>
> And this is the first matrix window, derived from the DEM, that
> multi.focal.function passes to returnfirstline:
>
> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [1,]   NA   NA   NA   NA   NA   NA
> NA [2,]   NA   NA   NA   NA   NA   NA   NA [3,]   NA   NA   NA   NA
> NA   NA   NA [4,]   NA   NA   NA   NA   NA   NA   NA [5,]   NA   NA
> NA  454  455  456  456 [6,]   NA   NA   NA  454  455  456  457 [7,]
> NA   NA   NA  454  454  456  457
>
> As you can see, the centre value of the matrix window is NA, which
> really should be the elevation 455 from the first row of the DEM.
>
> Any idea why this is happening, or am I just not understanding how to
> use multi.focal.function?
>
> Thanks,
>
> Nathan
>
> Nathan Odgers Postdoctoral Fellow—globalsoilmap.net West Virginia
> University Division of Plant and Soil Sciences National Soil Survey
> Center Geospatial Research Unit ph: +1 304 293 9839
>
> [[alternative HTML version deleted]]
>

-- 
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/