show.legend now handles named logical vectors (#2027)

* add support for vectors in show.legend

* fix behavior and add tests

* fix code after review

* update documentation and style

* fix NEWS.md

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 2.2.1.9000
 
+* The `show.legend` parameter now accepts a named logical vector to hide/show
+  only some aesthetics in the legend (@tutuchan, #1798)
+
 * Default colour maps for continuous data are controlled by global options
   `ggplot2.continuous.colour` and `ggplot2.continuous.fill`, which can be set to
   either `"gradient"` or `"viridis"` (@karawoo).

R/guide-legend.r

@@ -132,6 +132,13 @@
 #'
 #' # reversed order legend
 #' p + guides(col = guide_legend(reverse = TRUE))
+#'
+#' # hide some aesthetics from the legend
+#' p4 <- ggplot(mtcars, aes(mpg, qsec, colour = factor(vs), shape = factor(am))) +
+#'   geom_point()
+#' p4 + geom_line()
+#' p4 + geom_line(show.legend = c(color = FALSE))
+#'
 #' }
 guide_legend <- function(
 
@@ -249,7 +256,17 @@ guide_geom.legend <- function(guide, layers, default_mapping) {
 
     if (length(matched) > 0) {
       # This layer contributes to the legend
-      if (is.na(layer$show.legend) || layer$show.legend) {
+
+      # check if this layer should be included, different behaviour depending on
+      # if show.legend is a logical or a named logical vector
+      if (!is.null(names(layer$show.legend))) {
+        layer$show.legend <- rename_aes(layer$show.legend)
+        include <- is.na(layer$show.legend[matched]) || layer$show.legend[matched]
+      } else {
+        include <- is.na(layer$show.legend) || layer$show.legend
+      }
+
+      if (include) {
         # Default is to include it
 
         # Filter out set aesthetics that can't be applied to the legend

R/layer.r

@@ -31,6 +31,8 @@
 #' @param show.legend logical. Should this layer be included in the legends?
 #'   `NA`, the default, includes if any aesthetics are mapped.
 #'   `FALSE` never includes, and `TRUE` always includes.
+#'   It can also be a named logical vector to finely select the aesthetics to
+#'   display.
 #' @param inherit.aes If `FALSE`, overrides the default aesthetics,
 #'   rather than combining with them. This is most useful for helper functions
 #'   that define both data and aesthetics and shouldn't inherit behaviour from
@@ -76,8 +78,8 @@ layer <- function(geom = NULL, stat = NULL,
     show.legend <- params$show_guide
     params$show_guide <- NULL
   }
-  if (!is.logical(show.legend) || length(show.legend) != 1) {
-    warning("`show.legend` must be a logical vector of length 1.", call. = FALSE)
+  if (!is.logical(show.legend)) {
+    warning("`show.legend` must be a logical vector.", call. = FALSE)
     show.legend <- FALSE
   }