# inst/tinytest/test_lamW.R In lamW: Lambert-W Function

```# Test that functions return proper values
PrincipleBranchAnswers <- runif(5000, min = -1, max = 703.22703310477016)
SecondaryBranchAnswers <- runif(5000, min = -714.96865723796657, max = -1)

# Test that function behaves properly near 0
V0 <- seq(-2e-2, 2e-2, 2e-6)
V0E <- V0 * exp(V0)
LV0 <- lambertW0(V0E)

expect_equal(V0, LV0)

# Test that W0 behaves properly VERY close to 0
expect_equal(lambertW0(1e-275), 1e-275)
expect_equal(lambertW0(7e-48), 7e-48)
expect_equal(lambertW0(-3.81e-71), -3.81e-71)

# Test that function behaves properly near -1/e
expect_equal(lambertW0(-1/exp(1)), -1)
expect_equal(lambertWm1(-1/exp(1)), -1)

# Test that function behaves properly near asymptotes
L <- seq(1e-6 - exp(-1), -0.25, 3e-6)
V0 <- lambertW0(L)
Vm1 <- lambertWm1(L)

expect_equal(V0 * exp(V0), L)
expect_equal(Vm1 * exp(Vm1), L)

Vm1 <- seq(-714, -714.96865, -3e-5)
Vm1E <- Vm1 * exp(Vm1)
LVm1 <- lambertWm1(Vm1E)

expect_equal(Vm1, LVm1)

# Test that function behaves properly at asymptotes
expect_equal(lambertW0(Inf), Inf)
expect_equal(lambertWm1(0), -Inf)

# Test that NaNs are returned for values outside domain
expect_true(is.nan(lambertW0(-Inf)))
expect_true(is.nan(lambertWm1(-Inf)))
expect_true(is.nan(lambertWm1(Inf)))
expect_true(is.nan(lambertW0(-1)))
expect_true(is.nan(lambertWm1(-1)))
expect_true(is.nan(lambertWm1(1)))
expect_true(is.nan(lambertW0(c(1, -1)))[[2]])

# Test that integers are converted to reals for principle branch
expect_equal(lambertW0(c(-1L, 0L, 1L, 2L, 3L, 4L)),
lambertW0(c(-1, 0, 1, 2, 3, 4)))

## Test CITATION
expect_true(any(grepl(packageVersion('lamW'), toBibtex(citation('lamW')),
fixed = TRUE)))
```

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lamW documentation built on Jan. 19, 2022, 1:08 a.m.