find_transformation() returning multiple values (#972)

Fixes #971

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: insight
 Title: Easy Access to Model Information for Various Model Objects
-Version: 0.99.0.15
+Version: 0.99.0.16
 Authors@R:
     c(person(given = "Daniel",
              family = "Lüdecke",

NEWS.md

@@ -62,6 +62,9 @@
 
 * Fixed issue in `compact_character()` and `compact_list()` for date-variables.
 
+* Fixed edge case in `find_transformation()` for simple log-transformation of
+  the response variable.
+
 # insight 0.20.5
 
 ## General

R/find_transformation.R

@@ -102,15 +102,19 @@ find_transformation.character <- function(x, ...) {
     if (grepl("log\\(log\\((.*)\\)\\)", x)) {
       transform_fun <- "log-log"
     } else {
-      # 1. try: log(x + number)
-      plus_minus <- .safe(
-        eval(parse(text = gsub("log\\(([^,\\+)]*)(.*)\\)", "\\2", x)))
-      )
-      # 2. try: log(number + x)
-      if (is.null(plus_minus)) {
+      plus_minus <- NULL
+      # make sure we definitly have a "+" in the log-transformation
+      if (grepl("+", x, fixed = TRUE)) {
+        # 1. try: log(x + number)
         plus_minus <- .safe(
-          eval(parse(text = gsub("log\\(([^,\\+)]*)(.*)\\)", "\\1", x)))
+          eval(parse(text = gsub("log\\(([^,\\+)]*)(.*)\\)", "\\2", x)))
         )
+        # 2. try: log(number + x)
+        if (is.null(plus_minus)) {
+          plus_minus <- .safe(
+            eval(parse(text = gsub("log\\(([^,\\+)]*)(.*)\\)", "\\1", x)))
+          )
+        }
       }
       if (is.null(plus_minus) || is.function(plus_minus)) {
         transform_fun <- "log"

tests/testthat/test-find_transformation.R

@@ -132,3 +132,19 @@ test_that("find_transformation - detect powers", {
     )
   )
 })
+
+
+test_that("find_transformation - works with log-edge cases", {
+  set.seed(1)
+  n <- 30
+  x <- rlnorm(n = n, meanlog = 3, sdlog = 1)
+  y <- exp(2 + log(x) + rnorm(n, sd = 3))
+  d <- data.frame(x, y)
+  m <- lm(log(y) ~ log(x), data = d)
+
+  expect_identical(find_transformation(m), "log")
+  expect_identical(
+    find_transformation(m, include_all = TRUE),
+    list(response = c(y = "log"), conditional = c(x = "log"))
+  )
+})