## ----raster-1a----------------------------------------------------------------
library(terra)
x <- rast()
x


## ----raster-1aa---------------------------------------------------------------
x <- rast(ncol=36, nrow=18, xmin=-1000, xmax=1000, ymin=-100, ymax=900)
res(x)


## ----raster-1aaa--------------------------------------------------------------
res(x) <- 100
res(x)
ncol(x)
# change the numer of columns (affects resolution)
ncol(x) <- 18
ncol(x)
res(x)


## ----raster-1aaab-------------------------------------------------------------
crs(x) <- "+proj=utm +zone=48 +datum=WGS84"
x


## ----raster-1b, fig=TRUE , fig.height=3.5, fig.width=7------------------------
r <- rast(ncol=10, nrow=10)
ncell(r)
hasValues(r)

# use the 'values' function, e.g., 
values(r) <- 1:ncell(r)
# or
set.seed(0)
values(r) <- runif(ncell(r))

hasValues(r)
sources(r)
values(r)[1:10]

plot(r, main='Raster with 100 cells')


## ----raster-1c, echo=TRUE-----------------------------------------------------
hasValues(r)
res(r)
dim(r)
xmax(r)

# change the maximum x coordinate of the extent (bounding box) of the SpatRaster
xmax(r) <- 0

hasValues(r)
res(r)
dim(r)

ncol(r) <- 6
hasValues(r)
res(r)
dim(r)
xmax(r)


## ----raster-2a, fig=TRUE , echo=TRUE------------------------------------------
# get the name of an example file installed with the package
# do not use this construction of your own files
filename <- system.file("ex/meuse.tif", package="terra")
filename
r <- rast(filename)
sources(r)
hasValues(r)
plot(r, main='SpatRaster from file')


## ----raster-2b----------------------------------------------------------------
# create three identical SpatRaster objects
r1 <- r2 <- r3 <- rast(nrow=10, ncol=10)
# Assign random cell values 
values(r1) <- runif(ncell(r1))
values(r2) <- runif(ncell(r2))
values(r3) <- runif(ncell(r3))


## ----raster-2bb---------------------------------------------------------------
s <- c(r1, r2, r3)
s
nlyr(s)


## ----raster-2bbb--------------------------------------------------------------
filename <- system.file("ex/logo.tif", package="terra")
filename
b <- rast(filename)
b
nlyr(b)


## ----raster-2bbbb-------------------------------------------------------------
r <- b[[2]]