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

[Nathan Odgers]

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

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