1 files changed, 43 insertions, 0 deletions
diff --git a/tests/testthat/test_inverse.predict.R b/tests/testthat/test_inverse.predict.R
new file mode 100644
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--- /dev/null
+++ b/tests/testthat/test_inverse.predict.R
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+context("Inverse predictions")
+
+library(chemCal)
+
+test_that("Inverse predictions for unweighted regressions are stable", {
+  m1 <- lm(y ~ x, data = massart97ex1)
+
+  # Known values from chemcal Version 0.1-37
+  p1.1 <- inverse.predict(m1, 15)
+  expect_equal(signif(p1.1$Prediction, 7), 6.09381)
+  expect_equal(signif(p1.1$`Standard Error`, 7), 1.767278)
+  expect_equal(signif(p1.1$Confidence, 7), 4.906751)
+
+  p1.2 <- inverse.predict(m1, 90)
+  expect_equal(signif(p1.2$Prediction, 7), 43.93983)
+  expect_equal(signif(p1.2$`Standard Error`, 7), 1.767747)
+  expect_equal(signif(p1.2$Confidence, 7), 4.908053)
+
+  p1.3 <- inverse.predict(m1, rep(90, 5))
+  expect_equal(signif(p1.3$Prediction, 7), 43.93983)
+  expect_equal(signif(p1.3$`Standard Error`, 7), 1.141204)
+  expect_equal(signif(p1.3$Confidence, 7), 3.168489)
+})
+
+test_that("Inverse predictions for weighted regressions are stable", {
+  attach(massart97ex3)
+  yx <- split(y, x)
+  ybar <- sapply(yx, mean)
+  s <- round(sapply(yx, sd), digits = 2)
+  w <- round(1 / (s^2), digits = 3)
+  weights <- w[factor(x)]
+  m3 <- lm(y ~ x, w = weights)
+
+  p3.1 <- inverse.predict(m3, 15, ws = 1.67)
+  expect_equal(signif(p3.1$Prediction, 7), 5.865367)
+  expect_equal(signif(p3.1$`Standard Error`, 7), 0.8926109)
+  expect_equal(signif(p3.1$Confidence, 7), 2.478285)
+
+  p3.2 <- inverse.predict(m3, 90, ws = 0.145)
+  expect_equal(signif(p3.2$Prediction, 7), 44.06025)
+  expect_equal(signif(p3.2$`Standard Error`, 7), 2.829162)
+  expect_equal(signif(p3.2$Confidence, 7), 7.855012)
+})