RasterBrick coordinates in R

Question

I plotted a RasterBrick, but I want to know the coordinates of each corner. I see that xmin = 3263575, xmax = 3300872, etc., but how are those coordinates?
class      : RasterStack 
dimensions : 161, 161, 25921, 12  (nrow, ncol, ncell, nlayers)
resolution : 231.6564, 231.6564  (x, y)
extent     : 3263575, 3300872, -63010.57, -25713.9  (xmin, xmax, ymin, ymax)
crs        : +proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181 +b=6371007.181 +units=m +no_defs 
names      : X2010.01.01, X2010.01.17, X2010.02.02, X2010.02.18, X2010.03.06, X2010.03.22, X2010.04.07, X2010.04.23, X2010.05.09, X2010.05.25, X2010.06.10, X2010.06.26 
min values :        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3 
max values :      0.9825,      0.9545,      0.9787,      0.9893,      0.8823,      0.9836,      0.9428,      0.9922,      0.9841,      0.9547,      0.9576,      0.9652

JepsonNomad · Accepted Answer

The extent of that raster object is expressed in units according to the crs. So, to get "coordinates" (presumably you're looking for longitude and latitude) you need to create a spatial object with that extent information, and convert it to the desired crs. Based entirely off this answer, you can convert your extent of interest using the following:
library(sp)
library(raster)

ext <- extent(3263575, 3300872, -63010.57, -25713.9)
ext
# You could directly reference your own raster by uncommenting the next line
# ext <- extent(myRasterBrick)

ext <- as(ext, "SpatialPolygons")
sp::proj4string(ext) <- "+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181 +b=6371007.181 +units=m +no_defs"
# Similarly, use the proj info from your raster to assign crs to extent object
# sp::proj4string(ext) <- proj4string(myRasterBrick)

e.geo <- sp::spTransform(ext, CRS("+proj=longlat +datum=WGS84 +no_defs 
                             +ellps=WGS84 +towgs84=0,0,0"))
e.geo

Jeffrey Evans · Answer

Here is how you return the four corner coordinates of the raster extent. If you use sp::coordinates on the extent object then the polygon centroid coordinate is returned.
Here is an example of your raster, note that I do not have to assign a projection because everything will remain in the same projection space without it defined.
library(raster)
r <- raster(extent(3263575, 3300872, -63010.57, -25713.9),
            resolution=231.6564)
    r[] <- runif(ncell(r))

Now, create the extent polygon and then pull the node coordinates for the polygon.
e <- as(extent(r), "SpatialPolygons")  
  ( corner.coords <- e@polygons[[1]]@Polygons[[1]]@coords[1:4,] )

Now, the easy way. The sf::st_coordinates function returns polygon node coordinates and not centroids so we can do this in one fell swoop. Note that we are coercing the SpatialPolygons to an sf object in the same call. The index subsetting is removing two reference columns and the last coordinate pair that is the closing coordinate (same as the first) for the polygon.
sf::st_coordinates(as(as(extent(r), "SpatialPolygons"), "sf"))[1:4,][,1:2]

Lets plot the results and create a points feature class while we are at it.
p=SpatialPoints(sf::st_coordinates(as(as(extent(r), "SpatialPolygons"), "sf"))[1:4,][,1:2] )

plot(p,pch=19,cex=2)
  plot(r,add=TRUE)

RasterBrick coordinates in R

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