Avoid confusion in warning messages

The actual function call from which the warning is emitted might not be that helpful to the casual user.

Author: jiho

R/scale-brewer.r

@@ -71,7 +71,7 @@ scale_colour_distiller <- function(..., type = "seq", palette = 1, values = NULL
   # warn about using a qualitative brewer palette to generate the gradient
   type <- match.arg(type, c("seq", "div", "qual"))
   if (type == "qual") {
-    warning("Using a discrete colour palette in a continuous scale.\n  Consider using type = \"seq\" or type = \"div\" instead")
+    warning("Using a discrete colour palette in a continuous scale.\n  Consider using type = \"seq\" or type = \"div\" instead", call. = FALSE)
   }
   continuous_scale("colour", "distiller",
     gradient_n_pal(brewer_pal(type, palette)(6), values, space), na.value = na.value, ...)
@@ -83,7 +83,7 @@ scale_colour_distiller <- function(..., type = "seq", palette = 1, values = NULL
 scale_fill_distiller <- function(..., type = "seq", palette = 1, values = NULL, space = "Lab", na.value = "grey50") {
   type <- match.arg(type, c("seq", "div", "qual"))
   if (type == "qual") {
-    warning("Using a discrete colour palette in a continuous scale.\n  Consider using type = \"seq\" or type = \"div\" instead")
+    warning("Using a discrete colour palette in a continuous scale.\n  Consider using type = \"seq\" or type = \"div\" instead", call. = FALSE)
   }
   continuous_scale("fill", "distiller",
     gradient_n_pal(brewer_pal(type, palette)(6), values, space), na.value = na.value, ...)