Sample points uniformly from transformed space (#2095)

Fixes #1992

Author: thomasp85

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 2.2.1.9000
 
+* Fix bug in secondary axis that would lead to incorrectly placed ticks with
+  strong transforms (@thomasp85, #1992)
+
 * Fix `update_geom_defaults()` and `update_stat_defaults()` to allow American spelling of aesthetic parameters (@foo-bar-baz-qux, #2299).
 
 * Fixed bug when setting strips to `element_blank()` (@thomasp85). 

R/axis-secondary.R

@@ -114,10 +114,10 @@ AxisSecondary <- ggproto("AxisSecondary", NULL,
     if (self$empty()) return()
 
     # Get original range before transformation
-    inv_range <- scale$trans$inverse(range)
+    along_range <- seq(range[1], range[2], length.out = self$detail)
+    old_range <- scale$trans$inverse(along_range)
 
     # Create mapping between primary and secondary range
-    old_range <- seq(inv_range[1], inv_range[2], length.out = self$detail)
     full_range <- self$transform_range(old_range)
 
     # Test for monotonicity

tests/figs/deps.txt

@@ -1,3 +1,3 @@
-vdiffr: 0.1.1.9000
+vdiffr: 0.1.1
 svglite: 1.2.0.9001
 ggplot2: 2.2.1.9000