add check_installed("MASS") where appropriate

Author: teunbrand

R/stat-density-2d.R

@@ -138,6 +138,7 @@ StatDensity2d <- ggproto("StatDensity2d", Stat,
   contour_type = "lines",
 
   compute_layer = function(self, data, params, layout) {
+    check_installed("MASS", reason = "for calculating 2D density.")
     # first run the regular layer calculation to infer densities
     data <- ggproto_parent(Stat, self)$compute_layer(data, params, layout)
 

R/stat-ellipse.R

@@ -77,6 +77,14 @@ stat_ellipse <- function(mapping = NULL, data = NULL,
 StatEllipse <- ggproto("StatEllipse", Stat,
   required_aes = c("x", "y"),
 
+  setup_params = function(data, params) {
+    params$type <- params$type %||% "t"
+    if (identical(params$type, "t")) {
+      check_installed("MASS", "for calculating ellipses with `type = \"t\"`.")
+    }
+    params
+  },
+
   compute_group = function(data, scales, type = "t", level = 0.95,
                            segments = 51, na.rm = FALSE) {
     calculate_ellipse(data = data, vars = c("x", "y"), type = type,