Extract xy coordinates from raster of interesting neighborhood cells

Hi,

I'm not sure why you expect 24 points - you have 4 locations and for each you want the 4 bishop's directions - so, I think at most you should expect 16 points.  See http://www.lpc.uottawa.ca/publications/moransi/moran.htm <http://www.lpc.uottawa.ca/publications/moransi/moran.htm> for where I expect 4 points for bishop's for each input location; perhaps you have a different idea of bishop's direction?  

Your second point [45.12069, -88.369745] is on to the southern edge of the raster - so it can't find points southward - only the 2 northward.

Finally, it may not make any difference at all, but your pts_s has no coordinate reference.  Below I show where I assign the same projection as your raster.  I also don't have 'land_mask' so I reused 'r' and used xyFromCell to backwards extract the adjacent cell coordinates.

Does that do the trick for you?

Cheers,
Ben

### START
require(raster)
require(sp)

## Create a raster
r <- raster(nc=30, nr=30)
r <- setValues(r, round(runif(ncell(r))* 255))
plot(r)

##Given interesting points coordinates
xd     <- c( -24.99270,   45.12069,  99.40321,  73.64419)
yd     <- c(-45.435267, -88.369745, -7.086949, 44.174530)
pts <- data.frame(xd,yd)
pts_s<- SpatialPoints(pts)
projection(pts_s) <- projection(r)
points(pts_s, col="red", pch=16)

## Find pixels center of each point 
N_cells <- cellFromXY(r, pts_s)

e <- adjacent(r, N_cells , directions='bishop', id=TRUE, sorted = TRUE)
xy <- xyFromCell(r, e[,'to'], spatial = TRUE)

#Visualization

plot(r)
points(pts_s, col="red", pch=16)
points(xy, col="black", pch=16)
### END

Extract xy coordinates from raster of interesting neighborhood cells

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