[R-sig-Geo] Extract xy coordinates from raster of interesting neighborhood cells
ASANTOS
@lex@ndre@@nto@br @ending from y@hoo@com@br
Wed May 30 23:04:46 CEST 2018
Thanks so much Vijay and Ben, now it works!!!
Originally, I expect 24 for each 4 point (96 total).
Apologies, in my example preparation I changed the raster objects
'land_mask' and 'r' and the idea of my second point [45.12069,
-88.369745] is to force NA results.
The code below is a solution that I expected:
### Alternative to what Ben suggested!
## Set neighborhood matrix. Focal cell is 0 while neighbors are 1!!
neigh <- matrix(1L, nrow=5, ncol=5); neigh[3,3] <- 0L
e1<-adjacent(r, N_cells , directions=neigh, pairs=FALSE)
ng_coords1 <- xyFromCell(r, e1)
plot(r);
points(pts, col='red', pch=16);
points(ng_coords, col='black', pch=16);
points(ng_coords1, col='blue', pch=16)
### END
--
======================================================================
Alexandre dos Santos
Proteção Florestal
IFMT - Instituto Federal de Educação, Ciência e Tecnologia de Mato Grosso
Campus Cáceres
Caixa Postal 244
Avenida dos Ramires, s/n
Bairro: Distrito Industrial
Cáceres - MT CEP: 78.200-000
Fone: (+55) 65 99686-6970 (VIVO) (+55) 65 3221-2674 (FIXO)
alexandre.santos using cas.ifmt.edu.br
Lattes: http://lattes.cnpq.br/1360403201088680
OrcID: orcid.org/0000-0001-8232-6722
Researchgate: www.researchgate.net/profile/Alexandre_Santos10
LinkedIn: br.linkedin.com/in/alexandre-dos-santos-87961635
Mendeley:www.mendeley.com/profiles/alexandre-dos-santos6/
======================================================================
Em 30/05/2018 16:29, Vijay Lulla escreveu:
> Or you can try something like this?
>
> ### START
> require(raster)
> require(sp)
>
> r <- raster(nc=30, nr=30)
> r <- setValues(r, round(runif(ncell(r))* 255))
>
> 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)
>
> N_cells <- cellFromXY(r, pts_s)
> e<-adjacent(r, N_cells , directions='bishop', pairs=FALSE)
>
> ng_coords <- xyFromCell(r, e)
> plot(r)
> points(pts, col='red', pch=16)
> points(ng_coords, col='black', pch=16)
>
>
[[elided Yahoo spam]]
[[elided Yahoo spam]]
> neigh <- matrix(1L, nrow=5, ncol=5); neigh[3,3] <- 0L
> e1<-adjacent(r, N_cells , directions=neigh, pairs=FALSE)
> ng_coords1 <- xyFromCell(r, e1)
> plot(r);
> points(pts, col='red', pch=16);
> points(ng_coords, col='black', pch=16);
> points(ng_coords1, col='blue', pch=16)
> ### END
>
> HTH,
> Vijay.
>
> On Wed, May 30, 2018 at 4:22 PM, Ben Tupper <btupper using bigelow.org
> <mailto:btupper using bigelow.org>> wrote:
>
> 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>
> <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
>
>
>
>
>
> > On May 30, 2018, at 3:11 PM, ASANTOS via R-sig-Geo
> <r-sig-geo using r-project.org <mailto:r-sig-geo using r-project.org>> wrote:
> >
> > 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
> >
> > --
> >
> ======================================================================
> > Alexandre dos Santos
> > Proteção Florestal
> > IFMT - Instituto Federal de Educação, Ciência e Tecnologia de
> Mato Grosso
> > Campus Cáceres
> > Caixa Postal 244
> > Avenida dos Ramires, s/n
> > Bairro: Distrito Industrial
> > Cáceres - MT CEP: 78.200-000
> > Fone: (+55) 65 99686-6970 (VIVO) (+55) 65 3221-2674 (FIXO)
> >
> > alexandre.santos using cas.ifmt.edu.br
> <mailto:alexandre.santos using cas.ifmt.edu.br>
> > Lattes: http://lattes.cnpq.br/1360403201088680
> <http://lattes.cnpq.br/1360403201088680>
> > OrcID: orcid.org/0000-0001-8232-6722
> <http://orcid.org/0000-0001-8232-6722>
> > Researchgate: www.researchgate.net/profile/Alexandre_Santos10
> <http://www.researchgate.net/profile/Alexandre_Santos10>
> > LinkedIn: br.linkedin.com/in/alexandre-dos-santos-87961635
> <http://br.linkedin.com/in/alexandre-dos-santos-87961635>
> > Mendeley:www.mendeley.com/profiles/alexandre-dos-santos6/
> <http://www.mendeley.com/profiles/alexandre-dos-santos6/>
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo using r-project.org <mailto:R-sig-Geo using r-project.org>
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> <https://stat.ethz.ch/mailman/listinfo/r-sig-geo>
> >
>
> Ben Tupper
> Bigelow Laboratory for Ocean Sciences
> 60 Bigelow Drive, P.O. Box 380
> East Boothbay, Maine 04544
> http://www.bigelow.org
>
> Ecological Forecasting: https://eco.bigelow.org/
>
>
>
>
>
>
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>
>
> --
> Vijay Lulla, Ph.D.
>
> Assistant Professor,
> Dept. of Geography, IUPUI
> 425 University Blvd, CA-207C.
> Indianapolis, IN-46202
> vlulla using iupui.edu <mailto:vlulla using iupui.edu>
>
> <http://vijaylulla.com>
> http://vijaylulla.com
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