Variable sizes for geom_hex() (#6729)

* fix early exit

* exploit `hexbin::hexcoords(n)` arg

* add `radius` aesthetic

* use `radius` in hexagon construction

* add example

* add test

* add news bullet

Author: teunbrand

NEWS.md

@@ -9,6 +9,8 @@
   `grid::curveGrob()` (@fmarotta, #5998).
 * Fixed a regression where default `width` was miscalculated when some panels
   are empty (@teunbrand, #6758)
+* `geom_hex()` has a new `radius` aesthetic, representing the relative size of
+  the hexagons (@teunbrand, #6727)
 
 # ggplot2 4.0.1
 

R/geom-hex.R

@@ -5,10 +5,10 @@
 GeomHex <- ggproto("GeomHex", Geom,
   draw_group = function(self, data, panel_params, coord, lineend = "butt",
                         linejoin = "mitre", linemitre = 10) {
-    data <- fix_linewidth(data, snake_class(self))
     if (empty(data)) {
       return(zeroGrob())
     }
+    data <- fix_linewidth(data, snake_class(self))
 
     # Get hex sizes
     if (!is.null(data$width)) {
@@ -25,13 +25,12 @@ GeomHex <- ggproto("GeomHex", Geom,
       dy <- resolution(data$y, FALSE, TRUE) / sqrt(3) / 2 * 1.15
     }
 
-    hexC <- hexbin::hexcoords(dx, dy, n = 1)
-
     n <- nrow(data)
+    hexC <- hexbin::hexcoords(dx, dy, n = n)
 
-    hexdata <- data[rep(seq_len(n), each = 6), c("x", "y")]
-    hexdata$x <- rep.int(hexC$x, n) + hexdata$x
-    hexdata$y <- rep.int(hexC$y, n) + hexdata$y
+    hexdata <- vec_rep_each(data[c("x", "y", "radius")], times = 6L)
+    hexdata$x <- hexC$x * hexdata$radius + hexdata$x
+    hexdata$y <- hexC$y * hexdata$radius + hexdata$y
 
     coords <- coord$transform(hexdata, panel_params)
 
@@ -58,6 +57,7 @@ GeomHex <- ggproto("GeomHex", Geom,
     fill = from_theme(fill %||% col_mix(ink, paper)),
     linewidth = from_theme(borderwidth),
     linetype = from_theme(bordertype),
+    radius = 1,
     alpha = NA
   ),
 
@@ -95,5 +95,8 @@ GeomHex <- ggproto("GeomHex", Geom,
 #' # Or by specifying the width of the bins
 #' d + geom_hex(binwidth = c(1, 1000))
 #' d + geom_hex(binwidth = c(.1, 500))
+#'
+#' # The hexagons can be scaled by tuning the radius aesthetic
+#' d + geom_hex(aes(radius = after_stat(ncount)))
 #' }
 geom_hex <- make_constructor(GeomHex, stat = 'binhex')

man/geom_hex.Rd

@@ -27,6 +27,17 @@ test_that("bin size are picked up from stat", {
       geom_hex(aes(x = x, y = y), binwidth = c(0.1, 0.1)) +
       coord_cartesian(xlim = c(-1, 1), ylim = c(-1, 1))
   )
+
+  expect_doppelganger(
+    "hexes with different sizes",
+    ggplot(data.frame(x = 1:3, y = 0, r = (1:3)/6)) +
+      geom_hex(
+        aes(x = x, y = y, radius = r),
+        stat = "identity"
+      ) +
+      coord_cartesian(xlim = c(0, 4), y = c(-1, 1))
+  )
+
 })
 
 test_that("geom_hex works in non-linear coordinate systems", {