test_classify.R
In terra: Spatial Data Analysis

r <- rast(ncols=3, nrows=3)
set.seed(68)
values(r) <- runif(ncell(r)) # from example
# all values > 0 and <= 0.25 become 1, etc.
m <- c(0, 0.25, 1,  0.25, 0.5, 2,  0.5, 1, 3) # from example
rclmat <- matrix(m, ncol=3, byrow=TRUE)

rc <- classify(r, rclmat, include.lowest=TRUE)
expect_equal(as.vector(values(rc)), c(3, 3, 2, 3, 2, 3, 3, 1, 2))

values(r) <- (1:ncell(r))-1
m <- c(0, 2, 1,  2, 3, 2,  3, 8, 3) 
rclmat <- matrix(m, ncol=3, byrow=TRUE)
rc <- classify(r, rclmat, right=FALSE)
expect_equal(as.vector(values(rc)), c(1, 1, 2, 3, 3, 3, 3, 3, 8))

rc <- classify(r, rclmat, right=TRUE)
expect_equal(as.vector(values(rc)), c(0, 1, 1, 2, 3, 3, 3, 3, 3))

rc <- classify(r, rclmat, right=TRUE, include.lowest=TRUE)
expect_equal(as.vector(values(rc)), c(1, 1, 1, 2, 3, 3, 3, 3, 3))

# classify 2-column lookup
r <- rast(nrows=10, ncols=10, vals=sample(1:5, 100, replace=TRUE))
rcl <- data.frame(from=1:3, to=11:13)
r_opt <- classify(r, rcl)
v_opt <- as.vector(values(r_opt))
v_in <- as.vector(values(r))
expect_equal(v_opt[v_in == 1], rep(11, sum(v_in == 1)))
expect_equal(v_opt[v_in == 2], rep(12, sum(v_in == 2)))
expect_equal(v_opt[v_in == 3], rep(13, sum(v_in == 3)))
expect_equal(v_opt[v_in > 3], v_in[v_in > 3])