Improve scales behavior for ordered factors

DESCRIPTION

@@ -22,7 +22,8 @@ Imports:
     scales (>= 0.4.1.9002),
     stats,
     tibble,
-    lazyeval
+    lazyeval,
+    viridisLite
 Suggests:
     covr,
     ggplot2movies,
@@ -43,8 +44,7 @@ Suggests:
     rpart,
     rmarkdown,
     sf (>= 0.3-4),
-    svglite (>= 1.2.0.9001),
-    viridisLite
+    svglite (>= 1.2.0.9001)
 Remotes:
     hadley/scales,
     hadley/svglite

NAMESPACE

@@ -374,6 +374,7 @@ export(scale_alpha_datetime)
 export(scale_alpha_discrete)
 export(scale_alpha_identity)
 export(scale_alpha_manual)
+export(scale_alpha_ordinal)
 export(scale_color_brewer)
 export(scale_color_continuous)
 export(scale_color_discrete)
@@ -400,6 +401,7 @@ export(scale_colour_grey)
 export(scale_colour_hue)
 export(scale_colour_identity)
 export(scale_colour_manual)
+export(scale_colour_ordinal)
 export(scale_colour_viridis_c)
 export(scale_colour_viridis_d)
 export(scale_fill_brewer)
@@ -415,6 +417,7 @@ export(scale_fill_grey)
 export(scale_fill_hue)
 export(scale_fill_identity)
 export(scale_fill_manual)
+export(scale_fill_ordinal)
 export(scale_fill_viridis_c)
 export(scale_fill_viridis_d)
 export(scale_linetype)
@@ -428,6 +431,7 @@ export(scale_shape_continuous)
 export(scale_shape_discrete)
 export(scale_shape_identity)
 export(scale_shape_manual)
+export(scale_shape_ordinal)
 export(scale_size)
 export(scale_size_area)
 export(scale_size_continuous)
@@ -436,6 +440,7 @@ export(scale_size_datetime)
 export(scale_size_discrete)
 export(scale_size_identity)
 export(scale_size_manual)
+export(scale_size_ordinal)
 export(scale_type)
 export(scale_x_continuous)
 export(scale_x_date)

NEWS.md

@@ -1,5 +1,11 @@
 # ggplot2 2.2.1.9000
 
+* Ordered factors now behave differently from unordered factors in some cases.
+  Ordered factors throw a warning when mapped to shape (unordered factors do
+  not). Ordered factors do not throw warnings when mapped to size or alpha
+  (unordered factors do). Viridis is the default colour and fill scale for
+  ordered factors (@karawoo, #1526).
+
 * The `show.legend` parameter now accepts a named logical vector to hide/show
   only some aesthetics in the legend (@tutuchan, #1798)
 

R/scale-alpha.r

@@ -28,9 +28,20 @@ scale_alpha_continuous <- scale_alpha
 
 #' @rdname scale_alpha
 #' @export
-scale_alpha_discrete <- function(..., range = c(0.1, 1)) {
-  discrete_scale("alpha", "alpha_d",
-    function(n) seq(range[1], range[2], length.out = n), ...)
+scale_alpha_discrete <- function(...) {
+  warning("Using alpha for a discrete variable is not advised.", call. = FALSE)
+  scale_alpha_ordinal(...)
+}
+
+#' @rdname scale_alpha
+#' @export
+scale_alpha_ordinal <- function(..., range = c(0.1, 1)) {
+  discrete_scale(
+    "alpha",
+    "alpha_d",
+    function(n) seq(range[1], range[2], length.out = n),
+    ...
+  )
 }
 
 #' @rdname scale_alpha

R/scale-shape.r

@@ -43,6 +43,14 @@ scale_shape <- function(..., solid = TRUE) {
 #' @usage NULL
 scale_shape_discrete <- scale_shape
 
+#' @rdname scale_shape
+#' @export
+#' @usage NULL
+scale_shape_ordinal <- function(...) {
+  warning("Using shapes for an ordinal variable is not advised", call. = FALSE)
+  scale_shape(...)
+}
+
 #' @rdname scale_shape
 #' @export
 #' @usage NULL

R/scale-size.r

@@ -59,12 +59,24 @@ scale_size <- scale_size_continuous
 #' @rdname scale_size
 #' @export
 #' @usage NULL
-scale_size_discrete <- function(..., range = c(2, 6)) {
+scale_size_discrete <- function(...) {
   warning("Using size for a discrete variable is not advised.", call. = FALSE)
-  discrete_scale("size", "size_d", function(n) {
-    area <- seq(range[1] ^ 2, range[2] ^ 2, length.out = n)
-    sqrt(area)
-  }, ...)
+  scale_size_ordinal(...)
+}
+
+#' @rdname scale_size
+#' @export
+#' @usage NULL
+scale_size_ordinal <- function(..., range = c(2, 6)) {
+  discrete_scale(
+    "size",
+    "size_d",
+    function(n) {
+      area <- seq(range[1] ^ 2, range[2] ^ 2, length.out = n)
+      sqrt(area)
+    },
+    ...
+  )
 }
 
 #' @inheritDotParams continuous_scale -aesthetics -scale_name -palette -rescaler

R/zxx.r

@@ -5,6 +5,11 @@
 #' @usage NULL
 scale_colour_discrete <- scale_colour_hue
 
+#' @export
+#' @rdname scale_viridis
+#' @usage NULL
+scale_colour_ordinal <- scale_colour_viridis_d
+
 #' @export
 #' @rdname scale_gradient
 #' @usage NULL
@@ -48,6 +53,11 @@ scale_colour_date <- function(...,
 #' @usage NULL
 scale_fill_discrete <- scale_fill_hue
 
+#' @export
+#' @rdname scale_viridis
+#' @usage NULL
+scale_fill_ordinal <- scale_fill_viridis_d
+
 #' @export
 #' @rdname scale_gradient
 #' @usage NULL

tests/testthat/test-scales.r

@@ -188,3 +188,45 @@ test_that("Scales get their correct titles through layout", {
   expect_identical(p$layout$xlabel(p$plot$labels)$primary, "x")
   expect_identical(p$layout$ylabel(p$plot$labels)$primary, "y")
 })
+
+test_that("Size and alpha scales throw appropriate warnings for factors", {
+  df <- data.frame(
+    x = 1:3,
+    y = 1:3,
+    d = LETTERS[1:3],
+    o = factor(LETTERS[1:3], ordered = TRUE)
+  )
+  p <- ggplot(df, aes(x, y))
+
+  # There should be warnings when unordered factors are mapped to size/alpha
+  expect_warning(
+    ggplot_build(p + geom_point(aes(size = d))),
+    "Using size for a discrete variable is not advised."
+  )
+  expect_warning(
+    ggplot_build(p + geom_point(aes(alpha = d))),
+    "Using alpha for a discrete variable is not advised."
+  )
+  # There should be no warnings for ordered factors
+  expect_warning(ggplot_build(p + geom_point(aes(size = o))), NA)
+  expect_warning(ggplot_build(p + geom_point(aes(alpha = o))), NA) 
+})
+
+test_that("Shape scale throws appropriate warnings for factors", {
+  df <- data.frame(
+    x = 1:3,
+    y = 1:3,
+    d = LETTERS[1:3],
+    o = factor(LETTERS[1:3], ordered = TRUE)
+  )
+  p <- ggplot(df, aes(x, y))
+
+  # There should be no warnings when unordered factors are mapped to shape
+  expect_warning(ggplot_build(p + geom_point(aes(shape = d))), NA)
+
+  # There should be warnings for ordered factors
+  expect_warning(
+    ggplot_build(p + geom_point(aes(shape = o))),
+    "Using shapes for an ordinal variable is not advised"
+  )
+})

tests/testthat/test-viridis.R

@@ -1,6 +1,6 @@
 context("Viridis")
 
-df <- data.frame(x = 1, y = 1, z = "a")
+df <- data.frame(x = 1, y = 1, z = "a", tier = factor("low", ordered = TRUE))
 
 test_that("Viridis scale changes point color", {
   p1 <- ggplot(df, aes(x, y, colour = z)) +
@@ -10,3 +10,9 @@ test_that("Viridis scale changes point color", {
   expect_false(layer_data(p1)$colour == layer_data(p2)$colour)
   expect_equal(layer_data(p2)$colour, "#440154FF")
 })
+
+test_that("Viridis scale is used by default for ordered factors", {
+  p <- ggplot(df, aes(x, y, colour = tier)) + geom_point()
+
+  expect_equal(layer_data(p)$colour, "#440154FF")
+})