Use global options to control default continuous colour/fill scales

Author: karawoo

DESCRIPTION

@@ -170,6 +170,7 @@ Collate:
     'scale-.r'
     'scale-alpha.r'
     'scale-brewer.r'
+    'scale-colour.r'
     'scale-continuous.r'
     'scale-date.r'
     'scale-discrete-.r'

R/scale-colour.r

@@ -0,0 +1,46 @@
+#' Continuous colour scales
+#'
+#' Colour scales for continuous data default to the values of the
+#' `ggplot2.continuous.colour` and `ggplot2.continuous.fill` options. If these
+#' options are not present, ggplot2 will set them to `"gradient"`. See
+#' [options()] for more information.
+#' 
+#' @param ... Additional parameters passed on to the scale type
+#' @param type One of "gradient" (the default) or "viridis" indicating the
+#'   colour scale to use
+#' @seealso [scale_colour_gradient()], [scale_colour_viridis_c()],
+#'   [scale_fill_gradient()], and [scale_fill_viridis_c()]
+#' @export
+#' @rdname scale_colour_continuous
+#' @examples
+#' v <- ggplot(faithfuld, aes(waiting, eruptions, fill = density)) +
+#' geom_tile()
+#' v
+#' 
+#' v + scale_fill_continuous(type = "gradient")
+#' v + scale_fill_continuous(type = "viridis")
+#' 
+#' # The above are equivalent to
+#' v + scale_fill_gradient()
+#' v + scale_fill_viridis_c()
+scale_colour_continuous <- function(...,
+                                    type = getOption("ggplot2.continuous.colour")) {
+  switch(
+    type,
+    gradient = scale_colour_gradient(...),
+    viridis = scale_colour_viridis_c(...),
+    stop("Unknown scale type", call. = FALSE)
+  )
+}
+
+#' @rdname scale_colour_continuous
+#' @export
+scale_fill_continuous <- function(...,
+                                  type = getOption("ggplot2.continuous.fill")) {
+  switch(
+    type,
+    gradient = scale_fill_gradient(...),
+    viridis = scale_fill_viridis_c(...),
+    stop("Unknown scale type", call. = FALSE)
+  )
+}

R/zxx.r

@@ -5,11 +5,6 @@
 #' @usage NULL
 scale_colour_discrete <- scale_colour_hue
 
-#' @export
-#' @rdname scale_gradient
-#' @usage NULL
-scale_colour_continuous <- scale_colour_gradient
-
 #' @export
 #' @rdname scale_gradient
 #' @usage NULL
@@ -29,11 +24,6 @@ scale_colour_date <- function() {
 #' @usage NULL
 scale_fill_discrete <- scale_fill_hue
 
-#' @export
-#' @rdname scale_gradient
-#' @usage NULL
-scale_fill_continuous <- scale_fill_gradient
-
 #' @export
 #' @rdname scale_gradient
 #' @usage NULL

R/zzz.r

@@ -19,3 +19,15 @@ release_questions <- function() {
     "Have you built the book?"
   )
 }
+
+.onLoad <- function(libname, pkgname) {
+  op <- options()
+  op.ggplot2 <- list(
+    ggplot2.continuous.colour = "gradient",
+    ggplot2.continuous.fill = "gradient"
+  )
+  toset <- !(names(op.ggplot2) %in% names(op))
+  if(any(toset)) options(op.ggplot2[toset])
+
+  invisible()
+}