unique(<difftime>) now works, too

git-svn-id: https://svn.r-project.org/R/trunk@87667 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: maechler

doc/NEWS.Rd

@@ -188,6 +188,9 @@
 
       \item A \code{summary()} method for \code{"difftime"} objects which
       prints nicely, similar to those for \code{"Date"} and \code{"POSIXct"}.
+
+      \item \code{unique()}'s default method now also deals with
+      \code{"difftime"} objects.
     }
   }
 

src/library/base/R/duplicated.R

@@ -1,7 +1,7 @@
 #  File src/library/base/R/duplicated.R
 #  Part of the R package, https://www.R-project.org
 #
-#  Copyright (C) 1995-2018 The R Core Team
+#  Copyright (C) 1995-2025 The R Core Team
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -120,9 +120,11 @@ function(x, incomparables = FALSE, fromLast = FALSE, nmax = NA, ...)
     }
     z <- .Internal(unique(x, incomparables, fromLast, nmax))
     if(inherits(x, "POSIXct"))
-        structure(z, class = class(x), tzone = attr(x, "tzone"))
+        .POSIXct(z, attr(x, "tzone"), class(x))
     else if(inherits(x, "Date"))
-        structure(z, class = class(x))
+        .Date(z, class(x))
+    else if(inherits(x, "difftime"))
+        .difftime(z, attr(x,"units"), class(x))
     else z
 }
 

src/library/base/man/unique.Rd

@@ -79,6 +79,8 @@ unique(x, incomparables = FALSE, \dots)
   For a vector, an object of the same type of \code{x}, but with only
   one copy of each duplicated element.  No attributes are copied (so
   the result has no names).
+  The default method also keeps (number-like) date-time vectors of classes
+  \code{"\link{POSIXct}"}, \code{"\link{Date}"}, and \code{"\link{difftime}"}.
 
   For a data frame, a data frame is returned with the same columns but
   possibly fewer rows (and with row names from the first occurrences of

tests/reg-tests-1e.R

@@ -1800,6 +1800,12 @@ stopifnot(exprs = {
 ## summary(<difftime>) was not useful in R < 4.5.0
 
 
+## unique(<difftime>)
+(unidt <- unique(dt))
+stopifnot(inherits(unidt, "difftime"), length(unidt) <= 2) # '2': allow "inaccuracy"
+## unique() lost the class  in R < 4.5.0
+
+
 
 ## keep at end
 rbind(last =  proc.time() - .pt,