## -----------------------------------------------------------------------------
library(terra)
r <- rast(ncol=10, nrow=10, xmin=-150, xmax=-80, ymin=20, ymax=60)
r


## -----------------------------------------------------------------------------
values(r) <- runif(ncell(r))
r


## -----------------------------------------------------------------------------
values(r) <- 1:ncell(r)
r


## ---- plot4-1, fig.height=4---------------------------------------------------
plot(r)

# add polygon and points
lon <- c(-116.8, -114.2, -112.9, -111.9, -114.2, -115.4, -117.7)
lat <- c(41.3, 42.9, 42.4, 39.8, 37.6, 38.3, 37.6)
lonlat <- cbind(id=1, part=1, lon, lat)
pts <- vect(lonlat)
pols <- vect(lonlat, type="polygons", crs="+proj=longlat +datum=WGS84")

points(pts, col="red", pch=20, cex=3)
lines(pols, col="blue", lwd=2)


## ---- plot4-2, fig.height=6.8, fig.width=9------------------------------------
r2 <- r * r
r3  <- sqrt(r)
s <- c(r, r2, r3)
s
plot(s)