Fix bug in guide_axis_logticks(negative.small)

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* Better handling of the `guide_axis_logticks(negative.small)` parameter when
+  scale limits have small maximum (@teunbrand, #6121).
 * Fixed bug where the `ggplot2::`-prefix did not work with `stage()` 
   (@teunbrand, #6104).
 * New `get_labs()` function for retrieving completed plot labels 

R/guide-axis-logticks.R

@@ -17,6 +17,8 @@ NULL
 #'   keep the default `NULL` argument.
 #' @param negative.small When the scale limits include 0 or negative numbers,
 #'   what should be the smallest absolute value that is marked with a tick?
+#'   If `NULL` (default), will be the smallest of 0.1 or 0.1 times the absolute
+#'   scale maximum.
 #' @param short.theme A theme [element][element_line()] for customising the
 #'   display of the shortest ticks. Must be a line or blank element, and
 #'   it inherits from the `axis.minor.ticks` setting for the relevant position.
@@ -69,7 +71,7 @@ guide_axis_logticks <- function(
   mid   = 1.5,
   short = 0.75,
   prescale.base = NULL,
-  negative.small = 0.1,
+  negative.small = NULL,
   short.theme = element_line(),
   expanded = TRUE,
   cap = "none",
@@ -187,28 +189,27 @@ GuideAxisLogticks <- ggproto(
     # Reconstruct original range
     limits <- transformation$inverse(scale$get_limits())
     has_negatives <- any(limits <= 0)
-
-    if (!has_negatives) {
-      start <- floor(log10(min(limits))) - 1L
-      end   <- ceiling(log10(max(limits))) + 1L
-    } else {
-      params$negative_small <- params$negative_small %||% 0.1
-      start <- floor(log10(abs(params$negative_small)))
-      end   <- ceiling(log10(max(abs(limits)))) + 1L
+    if (has_negatives) {
+      large  <- max(abs(limits))
+      small  <- params$negative_small %||% min(c(1, large) * 0.1)
+      limits <- sort(c(small * 10, large))
     }
 
+    start <- floor(log10(min(limits))) - 1L
+    end   <- ceiling(log10(max(limits))) + 1L
+
     # Calculate tick marks
-    tens  <- 10^seq(start, end, by = 1)
+    tens  <- 10^seq(start, end, by = 1L)
     fives <- tens * 5
     ones  <- as.vector(outer(setdiff(2:9, 5), tens))
 
     if (has_negatives) {
       # Filter and mirror ticks around 0
-      tens  <- tens[tens >= params$negative_small]
+      tens  <- tens[tens >= small]
       tens  <- c(tens, -tens, 0)
-      fives <- fives[fives >= params$negative_small]
+      fives <- fives[fives >= small]
       fives <- c(fives, -fives)
-      ones  <- ones[ones >= params$negative_small]
+      ones  <- ones[ones >= small]
       ones  <- c(ones, -ones)
     }
 

tests/testthat/test-guides.R

@@ -470,6 +470,11 @@ test_that("guide_axis_logticks calculates appropriate ticks", {
   expect_equal(unlog, c(-rev(outcome), 0, outcome))
   expect_equal(key$.type, rep(c(1,2,3), c(7, 4, 28)))
 
+  # Test very small pseudo_log (#6121)
+  scale <- test_scale(transform_pseudo_log(sigma = 1e-5), c(0, 1e-10))
+  key   <- train_guide(guide_axis_logticks(), scale)$logkey
+  expect_gte(nrow(key), 1)
+
   # Test expanded argument
   scale <- test_scale(transform_log10(), c(20, 900))
   scale$continuous_range <- c(1, 3)