Create spatial polygon grid from spatial points in R

Question

I am trying to recreate a map in R. I need 2 by 5 degree grid cells across the contiguous United States, but plotted in Albers Equal Area. The result is a grid with curved lines and slightly variable grid size, so I assume I cannot use a raster. I am able to reproduce the points, but not the grid. How do I make grid (polygon) lines for these points?

library(raster)

e <- as(raster::extent(-125, -65, 25, 49), "SpatialPolygons")
grd_lrg <- as.data.frame(makegrid(e, "regular", cellsize = c(5,2)))
names(grd_lrg)       <- c("X", "Y")
coordinates(grd_lrg) <- c("X", "Y")

# add projection information to the empty grid
proj4string(grd_lrg) <- CRS("+init=epsg:4326")

# transform to equal area Albers USGS
grd_lrg <- spTransform(grd_lrg, CRS("+init=epsg:5070"))

# plot it
plot(grd_lrg)

If I create the grid in Arc Map using Create Fishnet (Data Management) with the WGS84 coordinate system and import it into R, I get a nice looking grid:

But converting it to Albers Equal Area with spTransform creates major distortions of the lines:

So I am thinking I need to convert the points to Albers first and then add the lines?

Answer 1

here is a solution using sf and sf::st_make_grid:

library(raster)
library(sf)

e <- as(raster::extent(-125, -65, 25, 49), "SpatialPolygons") %>% 
  st_as_sf()

grd_lrg <- st_make_grid(e, cellsize = c(5, 2)) %>%
  st_set_crs(4326) %>% 
  st_transform(5070)

plot(grd_lrg)

Answer 2

You can make a long/lat raster and transform

library(raster)
r <- raster(ext = extent(-125, -65, 25, 49), res=c(5,2))
values(r) <- 1:ncell(r)
rA <- projectRaster(r, crs="+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m")

But what you want seems to be

library(rgdal)
p <- rasterToPolygons(r) 
# or do:  p <- as(r, "SpatialPolygonsDataFrame")
pA <- spTransform(p, "+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m")


plot(rA, axes=FALSE, box=FALSE)
plot(pA, add=TRUE)