[R-sig-Geo] gdistance: costDistance with barriers

[karljarvis]

Hi all,
I am seeing confusing behavior from the costDistance function in gdistance.
In general, when cost is constant, cost distance increases linearly with
actual distance. However, in this example, it is not doing that for the
longest few distances. Am I missing something?
Karl

r <- raster(nrows=18, ncols=36) 
r[] <- 1
t <- transition(r,function(x) 1/mean(x),4)
p <- cbind(seq(-120,120,by=40),rep(0,7))
costDistance(t,p)

> costDistance(t,p)
   1  2  3  4  5  6
2  4               
3  8  4            
4 12  8  4         
5 16 12  8  4      
6 16 16 12  8  4   
7 12 16 16 12  8  4



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