3.4 Raster objects in R

The R package raster provides three main classes of raster object (more details here):

1. RasterLayer imports a single-layer (variable) raster,
2. RasterStack imports in one single object several single-layer (variable) rasters stored in one or different files,
3. RasterBrick imports in one single object several single-layer (variable) rasters stored in one single file.

Using RasterStack and RasterBrick requires that the geometry of all raster data is equal.

Package raster define three classes of rater object we detail below.

3.4.1 RasterLayer

library(raster)
val1 <- matrix(runif(100 * 100, 0, 10), ncol = 100, nrow = 100)
ras1 <- raster(
  val1,
  crs = CRS("+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"),
  xmn = -82, xmx = +80, ymn = +42, ymx = +44
)
class(ras1)

#R>  [1] "RasterLayer"
#R>  attr(,"package")
#R>  [1] "raster"

dim(ras1)

#R>  [1] 100 100   1

head(values(ras1))

#R>  [1] 0.4088394 4.4199565 3.4096969 8.3125694 7.5901618 5.2882679

projection(ras1)

#R>  [1] "+proj=longlat +datum=WGS84 +no_defs"

3.4.2 RasterStack and RasterBrick

http://www.rspatial.org/spatial/rst/4-rasterdata.html#rasterstack-and-rasterbrick

Let’s first create another raster (with the same CRS)

val2 <- matrix(rnorm(100 * 100), ncol = 100, nrow = 100)
ras2 <- raster(
  val2,
  crs = CRS("+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"),
  xmn = -82, xmx = +80, ymn = +42, ymx = +44
)
class(ras2)

#R>  [1] "RasterLayer"
#R>  attr(,"package")
#R>  [1] "raster"

Let’s stack() ras1 and ras2:

sta1 <- stack(ras1, ras2)
class(sta1)

#R>  [1] "RasterStack"
#R>  attr(,"package")
#R>  [1] "raster"

Let’s brick() them:

bri1 <- brick(ras1, ras2)
class(bri1)

#R>  [1] "RasterBrick"
#R>  attr(,"package")
#R>  [1] "raster"