[R-sig-Geo] Extract xy coordinates from raster of interesting neighborhood cells

[ASANTOS]

Dear R-Sig-Geo Members,

     I've like to extract xy coordinates from raster of 24 neigborhood 
cells that surround the 4 given points (pts_s) pixels and for this I used:

#Packages

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)
points(pts_s, col="red", pch=16)

## Find pixels center of each point (My idea is not to use the original 
point coordinates, but coordinates of the center of interesting pixel).
N_cells <- cellFromXY(r, pts_s)


# Extract xy coordinates from raster of 24 neighborhood cells given 
pixel number N_cells
e<-adjacent(r, N_cells , directions='bishop', id=TRUE)
coordinates(land_mask)[e[,1],] ## Doesn't return 24 neighborhood by 
N_cells object
ng_coords<-coordinates(land_mask)[e[,1],]
#

#Visualization

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

     But I don't have success because the ng_coords object is not a 24 
neighborhood cells of each point that I search. There are solution for this?

Thanks in advance,

Alexandre

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Alexandre dos Santos
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