Avoid issues with ave(). PR#18223, by Thomas Soeiro.

git-svn-id: https://svn.r-project.org/R/trunk@87749 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: hornik

src/library/base/R/interaction.R

@@ -17,7 +17,7 @@
 #  https://www.R-project.org/Licenses/
 
 ### This is almost like the Primitive ":" for factors
-### but with drop=TRUE, used in reshape
+### but with drop=TRUE, used in reshape and ave
 interaction <- function(..., drop = FALSE, sep = ".", lex.order = FALSE)
 {
     args <- list(...)

src/library/stats/R/ave.R

@@ -21,7 +21,7 @@ ave <- function (x, ..., FUN = mean)
     if(missing(...))
 	x[] <- FUN(x)
     else {
-	g <- interaction(...)
+	g <- interaction(..., drop = TRUE)
 	split(x,g) <- lapply(split(x, g), FUN)
     }
     x