data(volcano)
v <- raster(volcano, xmn=2667400, xmx=2668010, ymn=6478700, ymx=6479570, crs="+init=epsg:27200")
fd <- terrain(v, opt = "flowdir")
path <- flowPath(fd, 2407)
xy <- xyFromCell(fd, path)
plot(v)
lines(xy)
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