Minor ticks

NEWS.md

@@ -84,6 +84,7 @@
     * More informative error for mismatched 
      `direction`/`theme(legend.direction = ...)` arguments (#4364, #4930).
     * `guide_coloursteps()` and `guide_bins()` sort breaks (#5152).
+    * `guide_axis()` gains a `minor.ticks` argument to draw minor ticks (#4387).
     * `guide_axis()` gains a `cap` argument that can be used to trim the
       axis line to extreme breaks (#4907).
     * `guide_colourbar()` and `guide_coloursteps()` merge properly when one

R/guide-.R

@@ -351,7 +351,8 @@ Guide <- ggproto(
   },
 
   # Renders tickmarks
-  build_ticks = function(key, elements, params, position = params$position) {
+  build_ticks = function(key, elements, params, position = params$position,
+                         length = elements$ticks_length) {
 
     if (!is.list(key)) {
       breaks <- key
@@ -365,8 +366,7 @@ Guide <- ggproto(
       return(zeroGrob())
     }
 
-    tick_len <- rep(elements$ticks_length %||% unit(0.2, "npc"),
-                    length.out = n_breaks)
+    tick_len <- rep(length %||% unit(0.2, "npc"), length.out = n_breaks)
 
     # Resolve mark
     mark <- unit(rep(breaks, each = 2), "npc")
@@ -375,7 +375,7 @@ Guide <- ggproto(
     pos <- unname(c(top = 1, bottom = 0, left = 0, right = 1)[position])
     dir <- -2 * pos + 1
     pos <- unit(rep(pos, 2 * n_breaks), "npc")
-    dir <- rep(vec_interleave(0, dir), n_breaks) * tick_len
+    dir <- rep(vec_interleave(dir, 0), n_breaks) * tick_len
     tick <- pos + dir
 
     # Build grob

R/guide-axis.R

@@ -14,6 +14,8 @@
 #' @param n.dodge The number of rows (for vertical axes) or columns (for
 #'   horizontal axes) that should be used to render the labels. This is
 #'   useful for displaying labels that would otherwise overlap.
+#' @param minor.ticks Whether to draw the minor ticks (`TRUE`) or not draw
+#'   minor ticks (`FALSE`, default).
 #' @param cap A `character` to cut the axis line back to the last breaks. Can
 #'   be `"none"` (default) to draw the axis line along the whole panel, or
 #'   `"upper"` and `"lower"` to draw the axis to the upper or lower break, or
@@ -42,23 +44,23 @@
 #' # can also be used to add a duplicate guide
 #' p + guides(x = guide_axis(n.dodge = 2), y.sec = guide_axis())
 guide_axis <- function(title = waiver(), check.overlap = FALSE, angle = NULL,
-                       n.dodge = 1, cap = "none", order = 0,
-                       position = waiver()) {
-
+                       n.dodge = 1, minor.ticks = FALSE, cap = "none",
+                       order = 0, position = waiver()) {
+  check_bool(minor.ticks)
   if (is.logical(cap)) {
     check_bool(cap)
     cap <- if (cap) "both" else "none"
   }
   cap <- arg_match0(cap, c("none", "both", "upper", "lower"))
 
-
   new_guide(
     title = title,
 
     # customisations
     check.overlap = check.overlap,
     angle = angle,
     n.dodge = n.dodge,
+    minor.ticks = minor.ticks,
     cap = cap,
 
     # parameter
@@ -87,6 +89,7 @@ GuideAxis <- ggproto(
     direction = NULL,
     angle     = NULL,
     n.dodge   = 1,
+    minor.ticks = FALSE,
     cap       = "none",
     order     = 0,
     check.overlap = FALSE
@@ -100,9 +103,26 @@ GuideAxis <- ggproto(
     line  = "axis.line",
     text  = "axis.text",
     ticks = "axis.ticks",
-    ticks_length = "axis.ticks.length"
+    minor = "axis.minor.ticks",
+    major_length = "axis.ticks.length",
+    minor_length = "axis.minor.ticks.length"
   ),
 
+  extract_key = function(scale, aesthetic, minor.ticks, ...) {
+    major <- Guide$extract_key(scale, aesthetic, ...)
+    if (!minor.ticks) {
+      return(major)
+    }
+    if (!is.null(major)) {
+      major$.type <- "major"
+    }
+    minor <- setdiff(scale$get_breaks_minor(), major$.value)
+    new_scale <- ggproto(NULL, scale, breaks = minor, get_labels = .no_labels)
+    minor <- Guide$extract_key(new_scale, aesthetic, ...)
+    minor$.type <- "minor"
+    vec_rbind(major, minor)
+  },
+
   extract_params = function(scale, params, ...) {
     params$name <- paste0(params$name, "_", params$aesthetic)
     params
@@ -190,7 +210,7 @@ GuideAxis <- ggproto(
   },
 
   setup_elements = function(params, elements, theme) {
-    axis_elem <- c("line", "text", "ticks", "ticks_length")
+    axis_elem <- c("line", "text", "ticks", "minor", "major_length", "minor_length")
     is_char  <- vapply(elements[axis_elem], is.character, logical(1))
     axis_elem <- axis_elem[is_char]
     elements[axis_elem] <- lapply(
@@ -230,15 +250,6 @@ GuideAxis <- ggproto(
       "horizontal"
     }
 
-    # TODO: delete following comment at some point:
-    # I found the 'position_*'/'non-position_*' and '*_dim' names confusing.
-    # For my own understanding, these have been renamed as follows:
-    # * 'aes' and 'orth_aes' for the aesthetic direction and the direction
-    #   orthogonal to the aesthetic direction, respectively.
-    # * 'para_sizes' and 'orth_size(s)' for the dimension parallel to the
-    #   aesthetic and orthogonal to the aesthetic respectively.
-    # I also tried to trim down the verbosity of the variable names a bit
-
     new_params <- c("aes", "orth_aes", "para_sizes", "orth_size", "orth_sizes",
                     "vertical", "measure_gtable", "measure_text")
     if (direction == "vertical") {
@@ -280,7 +291,33 @@ GuideAxis <- ggproto(
     )
   },
 
+  build_ticks = function(key, elements, params, position = params$opposite) {
+
+    major <- Guide$build_ticks(
+      vec_slice(key, (key$.type %||% "major") == "major"),
+      elements, params, position,
+      elements$major_length
+    )
+
+    if (!params$minor.ticks || inherits(elements$minor, "element_blank")) {
+      return(major)
+    }
+
+    elements$ticks <- elements$minor
+    minor <- Guide$build_ticks(
+      vec_slice(key, (key$.type %||% "major") == "minor"),
+      elements, params, position,
+      elements$minor_length
+    )
+    grobTree(major, minor, name = "ticks")
+  },
+
   build_labels = function(key, elements, params) {
+
+    if (".type" %in% names(key)) {
+      key <- vec_slice(key, key$.type == "major")
+    }
+
     labels   <- validate_labels(key$.label)
     n_labels <- length(labels)
 
@@ -314,9 +351,21 @@ GuideAxis <- ggproto(
 
     measure <- params$measure_text
 
-    length <- elements$ticks_length
-    spacer <- max(unit(0, "pt"), -1 * length)
-    labels <- do.call(unit.c, lapply(grobs$labels, measure))
+    # Ticks
+    range <- range(
+      0, convertUnit(elements$major_length, "cm", valueOnly = TRUE)
+    )
+    if (params$minor.ticks && !inherits(elements$minor, "element_blank")) {
+      range <- range(
+        range, convertUnit(elements$minor_length, "cm", valueOnly = TRUE)
+      )
+    }
+
+    length <- unit(range[2], "cm")
+    spacer <- max(unit(0, "pt"), unit(-1 * diff(range), "cm"))
+
+    # Text
+    labels <- do.call(unit.c, lapply(grobs$label, measure))
     title  <- measure(grobs$title)
 
     sizes <- unit.c(length, spacer, labels, title)
@@ -540,3 +589,5 @@ axis_label_element_overrides <- function(axis_position, angle = NULL) {
     ))
   }
 }
+
+.no_labels = function(...) NULL

R/theme-defaults.R

@@ -147,6 +147,7 @@ theme_grey <- function(base_size = 11, base_family = "",
     axis.ticks.length.y = NULL,
     axis.ticks.length.y.left = NULL,
     axis.ticks.length.y.right = NULL,
+    axis.minor.ticks.length = rel(0.75),
     axis.title.x =       element_text(
                            margin = margin(t = half_line / 2),
                            vjust = 1
@@ -478,6 +479,7 @@ theme_void <- function(base_size = 11, base_family = "",
     axis.ticks.length.y = NULL,
     axis.ticks.length.y.left = NULL,
     axis.ticks.length.y.right = NULL,
+    axis.minor.ticks.length = unit(0, "pt"),
     legend.box =         NULL,
     legend.key.size =    unit(1.2, "lines"),
     legend.position =    "right",
@@ -559,6 +561,7 @@ theme_test <- function(base_size = 11, base_family = "",
     axis.ticks.length.y = NULL,
     axis.ticks.length.y.left = NULL,
     axis.ticks.length.y.right = NULL,
+    axis.minor.ticks.length = rel(0.75),
     axis.title.x =       element_text(
                            margin = margin(t = half_line / 2),
                            vjust = 1

R/theme-elements.R

@@ -441,32 +441,57 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   axis.line.y         = el_def("element_line", "axis.line"),
   axis.line.y.left    = el_def("element_line", "axis.line.y"),
   axis.line.y.right   = el_def("element_line", "axis.line.y"),
+
   axis.text.x         = el_def("element_text", "axis.text"),
   axis.text.x.top     = el_def("element_text", "axis.text.x"),
   axis.text.x.bottom  = el_def("element_text", "axis.text.x"),
   axis.text.y         = el_def("element_text", "axis.text"),
   axis.text.y.left    = el_def("element_text", "axis.text.y"),
   axis.text.y.right   = el_def("element_text", "axis.text.y"),
+
   axis.ticks.length   = el_def("unit"),
   axis.ticks.length.x = el_def(c("unit", "rel"), "axis.ticks.length"),
   axis.ticks.length.x.top = el_def(c("unit", "rel"), "axis.ticks.length.x"),
   axis.ticks.length.x.bottom = el_def(c("unit", "rel"), "axis.ticks.length.x"),
   axis.ticks.length.y  = el_def(c("unit", "rel"), "axis.ticks.length"),
   axis.ticks.length.y.left = el_def(c("unit", "rel"), "axis.ticks.length.y"),
   axis.ticks.length.y.right = el_def(c("unit", "rel"), "axis.ticks.length.y"),
+
   axis.ticks.x        = el_def("element_line", "axis.ticks"),
   axis.ticks.x.top    = el_def("element_line", "axis.ticks.x"),
   axis.ticks.x.bottom = el_def("element_line", "axis.ticks.x"),
   axis.ticks.y        = el_def("element_line", "axis.ticks"),
   axis.ticks.y.left   = el_def("element_line", "axis.ticks.y"),
   axis.ticks.y.right  = el_def("element_line", "axis.ticks.y"),
+
   axis.title.x        = el_def("element_text", "axis.title"),
   axis.title.x.top    = el_def("element_text", "axis.title.x"),
   axis.title.x.bottom = el_def("element_text", "axis.title.x"),
   axis.title.y        = el_def("element_text", "axis.title"),
   axis.title.y.left   = el_def("element_text", "axis.title.y"),
   axis.title.y.right  = el_def("element_text", "axis.title.y"),
 
+  axis.minor.ticks.x.top    = el_def("element_line", "axis.ticks.x.top"),
+  axis.minor.ticks.x.bottom = el_def("element_line", "axis.ticks.x.bottom"),
+  axis.minor.ticks.y.left   = el_def("element_line", "axis.ticks.y.left"),
+  axis.minor.ticks.y.right  = el_def("element_line", "axis.ticks.y.right"),
+
+  axis.minor.ticks.length = el_def(c("unit", "rel")),
+  axis.minor.ticks.length.x = el_def(c("unit", "rel"), "axis.minor.ticks.length"),
+  axis.minor.ticks.length.x.top = el_def(
+    c("unit", "rel"), c("axis.minor.ticks.length.x", "axis.ticks.length.x.top")
+  ),
+  axis.minor.ticks.length.x.bottom = el_def(
+    c("unit", "rel"), c("axis.minor.ticks.length.x", "axis.ticks.length.x.bottom")
+  ),
+  axis.minor.ticks.length.y = el_def(c("unit", "rel"), "axis.minor.ticks.length"),
+  axis.minor.ticks.length.y.left = el_def(
+    c("unit", "rel"), c("axis.minor.ticks.length.y", "axis.ticks.length.y.left")
+  ),
+  axis.minor.ticks.length.y.right = el_def(
+    c("unit", "rel"), c("axis.minor.ticks.length.y", "axis.ticks.length.y.right")
+  ),
+
   legend.background   = el_def("element_rect", "rect"),
   legend.margin       = el_def("margin"),
   legend.spacing      = el_def("unit"),

R/theme.R

@@ -48,8 +48,13 @@
 #'   `axis.ticks.y.left`, `axis.ticks.y.right`). `axis.ticks.*.*` inherits from
 #'   `axis.ticks.*` which inherits from `axis.ticks`, which in turn inherits
 #'   from `line`
+#' @param axis.minor.ticks.x.top,axis.minor.ticks.x.bottom,axis.minor.ticks.y.left,axis.minor.ticks.y.right,
+#'   minor tick marks along axes ([element_line()]). `axis.minor.ticks.*.*`
+#'   inherit from the corresponding major ticks `axis.ticks.*.*`.
 #' @param axis.ticks.length,axis.ticks.length.x,axis.ticks.length.x.top,axis.ticks.length.x.bottom,axis.ticks.length.y,axis.ticks.length.y.left,axis.ticks.length.y.right
 #'   length of tick marks (`unit`)
+#' @param axis.minor.ticks.length,axis.minor.ticks.length.x,axis.minor.ticks.length.x.top,axis.minor.ticks.length.x.bottom,axis.minor.ticks.length.y,axis.minor.ticks.length.y.left,axis.minor.ticks.length.y.right
+#'   length of minor tick marks (`unit`), or relative to `axis.ticks.length` when provided with `rel()`.
 #' @param axis.line,axis.line.x,axis.line.x.top,axis.line.x.bottom,axis.line.y,axis.line.y.left,axis.line.y.right
 #'   lines along axes ([element_line()]). Specify lines along all axes (`axis.line`),
 #'   lines for each plane (using `axis.line.x` or `axis.line.y`), or individually
@@ -302,13 +307,24 @@ theme <- function(line,
                   axis.ticks.y,
                   axis.ticks.y.left,
                   axis.ticks.y.right,
+                  axis.minor.ticks.x.top,
+                  axis.minor.ticks.x.bottom,
+                  axis.minor.ticks.y.left,
+                  axis.minor.ticks.y.right,
                   axis.ticks.length,
                   axis.ticks.length.x,
                   axis.ticks.length.x.top,
                   axis.ticks.length.x.bottom,
                   axis.ticks.length.y,
                   axis.ticks.length.y.left,
                   axis.ticks.length.y.right,
+                  axis.minor.ticks.length,
+                  axis.minor.ticks.length.x,
+                  axis.minor.ticks.length.x.top,
+                  axis.minor.ticks.length.x.bottom,
+                  axis.minor.ticks.length.y,
+                  axis.minor.ticks.length.y.left,
+                  axis.minor.ticks.length.y.right,
                   axis.line,
                   axis.line.x,
                   axis.line.x.top,