✨ Using date breaks/minor breaks/labels in time scales. (#6282)

* Allow `transform = "hms"` in `datetime_scale()`

* add date arguments to time scales

* use `datetime_scale()` in time scales

* allow for additional underscore args

* inherit position scale

* `label_time()` can handle both <POSIXt> *and* <difftime> classes

* add test

* add news bullet

* redocument

* work in a skip

* Revert "`label_time()` can handle both <POSIXt> *and* <difftime> classes"

This reverts commit adcd2cb.

* separate labelling logic

Author: teunbrand

NEWS.md

@@ -296,6 +296,8 @@
 * All scales now expose the `aesthetics` parameter (@teunbrand, #5841)
 * New `theme(legend.key.justification)` to control the alignment of legend keys 
   (@teunbrand, #3669). 
+* Added `scale_{x/y}_time(date_breaks, date_minor_breaks, date_labels)` 
+  (@teunbrand, #4335).
 
 # ggplot2 3.5.1
 

R/scale-date.R

@@ -223,8 +223,11 @@ scale_y_datetime <- function(name = waiver(),
 #' @rdname scale_date
 scale_x_time <- function(name = waiver(),
                          breaks = waiver(),
+                         date_breaks = waiver(),
                          minor_breaks = waiver(),
+                         date_minor_breaks = waiver(),
                          labels = waiver(),
+                         date_labels = waiver(),
                          limits = NULL,
                          expand = waiver(),
                          oob = censor,
@@ -233,29 +236,37 @@ scale_x_time <- function(name = waiver(),
                          position = "bottom",
                          sec.axis = waiver()) {
 
-  scale_x_continuous(
+  sc <- datetime_scale(
+    ggplot_global$x_aes,
+    "hms",
     name = name,
+    palette = identity,
     breaks = breaks,
+    date_breaks = date_breaks,
     labels = labels,
+    date_labels = date_labels,
     minor_breaks = minor_breaks,
+    date_minor_breaks = date_minor_breaks,
+    guide = guide,
     limits = limits,
     expand = expand,
     oob = oob,
-    na.value = na.value,
-    guide = guide,
-    position = position,
-    transform = scales::transform_hms(),
-    sec.axis = sec.axis
+    position = position
   )
+
+  set_sec_axis(sec.axis, sc)
 }
 
 
 #' @rdname scale_date
 #' @export
 scale_y_time <- function(name = waiver(),
                          breaks = waiver(),
+                         date_breaks = waiver(),
                          minor_breaks = waiver(),
+                         date_minor_breaks = waiver(),
                          labels = waiver(),
+                         date_labels = waiver(),
                          limits = NULL,
                          expand = waiver(),
                          oob = censor,
@@ -264,20 +275,25 @@ scale_y_time <- function(name = waiver(),
                          position = "left",
                          sec.axis = waiver()) {
 
-  scale_y_continuous(
+  sc <- datetime_scale(
+    ggplot_global$y_aes,
+    "hms",
     name = name,
+    palette = identity,
     breaks = breaks,
+    date_breaks = date_breaks,
     labels = labels,
+    date_labels = date_labels,
     minor_breaks = minor_breaks,
+    date_minor_breaks = date_minor_breaks,
+    guide = guide,
     limits = limits,
     expand = expand,
     oob = oob,
-    na.value = na.value,
-    guide = guide,
-    position = position,
-    transform = scales::transform_hms(),
-    sec.axis = sec.axis
+    position = position
   )
+
+  set_sec_axis(sec.axis, sc)
 }
 
 #' Date/time scale constructor
@@ -312,9 +328,13 @@ datetime_scale <- function(aesthetics, transform, trans = deprecated(),
   }
   if (!is.waiver(date_labels)) {
     check_string(date_labels)
-    labels <- function(self, x) {
-      tz <- self$timezone %||% "UTC"
-      label_date(date_labels, tz)(x)
+    if (transform == "hms") {
+      labels <- label_time(date_labels)
+    } else {
+      labels <- function(self, x) {
+        tz <- self$timezone %||% "UTC"
+        label_date(date_labels, tz)(x)
+      }
     }
   }
 
@@ -324,15 +344,17 @@ datetime_scale <- function(aesthetics, transform, trans = deprecated(),
     scale_class <- switch(
       transform,
       date = ScaleContinuousDate,
-      time = ScaleContinuousDatetime
+      time = ScaleContinuousDatetime,
+      ScaleContinuousPosition
     )
   } else {
     scale_class <- ScaleContinuous
   }
 
   transform <- switch(transform,
     date = transform_date(),
-    time = transform_time(timezone)
+    time = transform_time(timezone),
+    hms  = transform_hms()
   )
 
   sc <- continuous_scale(

man/scale_date.Rd

@@ -143,7 +143,8 @@
       [4] "date_minor_breaks"
       
       $scale_x_time
-      [1] "minor_breaks"
+      [1] "date_breaks"       "minor_breaks"      "date_minor_breaks"
+      [4] "date_labels"      
       
       $scale_y_continuous
       [1] "minor_breaks"
@@ -157,7 +158,8 @@
       [4] "date_minor_breaks"
       
       $scale_y_time
-      [1] "minor_breaks"
+      [1] "date_breaks"       "minor_breaks"      "date_minor_breaks"
+      [4] "date_labels"      
       
       $sf_transform_xy
       [1] "target_crs"          "source_crs"          "authority_compliant"

tests/testthat/_snaps/prohibited-functions.md

@@ -47,6 +47,20 @@ test_that("not cached across calls", {
   expect_equal(get_panel_scales(p2)$x$timezone, "Australia/Lord_Howe")
 })
 
+test_that("time scale date breaks and labels work", {
+  skip_if_not_installed("hms")
+
+  d <- c(base_time(), base_time() + 5 * 24 * 3600) - base_time()
+
+  sc <- scale_x_time(date_breaks = "1 day", date_labels = "%d")
+  sc$train(d)
+
+  breaks <- sc$get_breaks()
+  expect_length(breaks, 6)
+  labels <- sc$get_labels(breaks)
+  expect_equal(labels, paste0("0", 1:6))
+})
+
 test_that("datetime size scales work", {
   p <- ggplot(df, aes(y = y)) + geom_point(aes(time1, size = time1))