library("segregation")
context("test_entropy")

test_that("custom log function", {
    expect_equal(logf(2, exp(1)), log(2))
})

test_that("correct entropy calculation", {
    expect_equal(entropy(data.frame(x = c(1)), "x"), 0)
    expect_equal(entropy(data.frame(x = c(1, 2)), "x"), log(2))
    expect_equal(entropy(data.frame(x = c(1, 2, 3)), "x"), log(3))

    expect_equal(
        entropy(data.frame(x = c(1, 2), n = c(10, 10)), "x", weight = "n"),
        log(2)
    )
    expect_equal(
        entropy(data.frame(x = c(1, 2), n = c(10, 10)), "x", weight = "n", base = 2),
        1
    )
    expect_equal(
        entropy(data.frame(x = c(1, 2), n = c(10, 30)), "x", weight = "n"),
        .25 * log(1 / .25) + .75 * log(1 / .75)
    )
})