From fa854e6feba27547122237c4ea7397a7220dc9d9 Mon Sep 17 00:00:00 2001
From: Hiroaki Yutani <yutani.ini@gmail.com>
Date: Thu, 11 Aug 2022 09:06:48 +0900
Subject: [PATCH] Add an example for stat_align()

---
 R/geom-ribbon.r    | 16 ++++++++++++++++
 man/geom_ribbon.Rd | 16 ++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/R/geom-ribbon.r b/R/geom-ribbon.r
index 2c8e1ba641..ed6f058452 100644
--- a/R/geom-ribbon.r
+++ b/R/geom-ribbon.r
@@ -41,6 +41,22 @@
 #' h +
 #'   geom_ribbon(aes(ymin = level - 1, ymax = level + 1), fill = "grey70") +
 #'   geom_line(aes(y = level))
+#'
+#' # The underlying stat_align() takes care of unaligned data points
+#' df <- data.frame(
+#'   g = c("a", "a", "a", "b", "b", "b"),
+#'   x = c(1, 3, 5, 2, 4, 6),
+#'   y = c(2, 5, 1, 3, 6, 7)
+#' )
+#' a <- ggplot(df, aes(x, y, fill = g)) +
+#'   geom_area()
+#'
+#' # Two groups have points on different X values.
+#' a + geom_point(size = 8) + facet_grid(g ~ .)
+#'
+#' # stat_align() interpolates and aligns the value so that the areas can stack
+#' # properly.
+#' a + geom_point(stat = "align", position = "stack", size = 8)
 geom_ribbon <- function(mapping = NULL, data = NULL,
                         stat = "identity", position = "identity",
                         ...,
diff --git a/man/geom_ribbon.Rd b/man/geom_ribbon.Rd
index 747333c503..85d54971c6 100644
--- a/man/geom_ribbon.Rd
+++ b/man/geom_ribbon.Rd
@@ -158,6 +158,22 @@ h + geom_area(aes(x = level, y = year), orientation = "y")
 h +
   geom_ribbon(aes(ymin = level - 1, ymax = level + 1), fill = "grey70") +
   geom_line(aes(y = level))
+
+# The underlying stat_align() takes care of unaligned data points
+df <- data.frame(
+  g = c("a", "a", "a", "b", "b", "b"),
+  x = c(1, 3, 5, 2, 4, 6),
+  y = c(2, 5, 1, 3, 6, 7)
+)
+a <- ggplot(df, aes(x, y, fill = g)) +
+  geom_area()
+
+# Two groups have points on different X values.
+a + geom_point(size = 8) + facet_grid(g ~ .)
+
+# stat_align() interpolates and aligns the value so that the areas can stack
+# properly.
+a + geom_point(stat = "align", position = "stack", size = 8)
 }
 \seealso{
 \code{\link[=geom_bar]{geom_bar()}} for discrete intervals (bars),