Add summary() method for difftime objects (Rd \alias already committe…

…d in c87594).

git-svn-id: https://svn.r-project.org/R/trunk@87599 00db46b3-68df-0310-9c12-caf00c1e9a41

src/library/base/R/datetime.R

@@ -940,6 +940,19 @@ function(..., recursive = FALSE)
 function(x, value)
     .difftime(NextMethod(), attr(x, "units"), oldClass(x))
 
+## Added in R 4.5.0.
+summary.difftime <-
+function(object, digits = getOption("digits"), ...)
+{
+    x <- summary.default(unclass(object), digits = digits, ...)
+    if(m <- match("NA's", names(x), 0L)) {
+        NAs <- as.integer(x[m])
+        x <- x[-m]
+        attr(x, "NAs") <- NAs
+    }
+    .difftime(x, attr(object, "units"), oldClass(object))
+}    
+
 ## ----- convenience functions -----
 
 seq.POSIXt <-

src/library/base/R/zzz.R

@@ -636,6 +636,7 @@ matrix(c("!", "hexmode",
          "summary", "connection",
          "summary", "data.frame",
          "summary", "default",
+         "summary", "difftime",
          "summary", "factor",
          "summary", "matrix",
          "summary", "proc_time",