Add ties.method="last" to frank (#4242)

NEWS.md

@@ -73,6 +73,8 @@ unit = "s")
 
 10. The dimensions of objects in a `list` column are now displayed, [#3671](https://github.com/Rdatatable/data.table/issues/3671). Thanks to @randomgambit for the request, and Tyson Barrett for the PR.
 
+11. `frank` gains `ties.method='last'`, paralleling the same in `base::order` which has been available since R 3.3.0 (April 2016), [#1689](https://github.com/Rdatatable/data.table/issues/1689). Thanks @abudis for the encouragement to accommodate this.
+
 ## BUG FIXES
 
 1. A NULL timezone on POSIXct was interpreted by `as.IDate` and `as.ITime` as UTC rather than the session's default timezone (`tz=""`) , [#4085](https://github.com/Rdatatable/data.table/issues/4085).

R/frank.R

@@ -1,4 +1,4 @@
-frankv = function(x, cols=seq_along(x), order=1L, na.last=TRUE, ties.method=c("average", "first", "random", "max", "min", "dense")) {
+frankv = function(x, cols=seq_along(x), order=1L, na.last=TRUE, ties.method=c("average", "first", "last", "random", "max", "min", "dense")) {
   ties.method = match.arg(ties.method)
   if (!length(na.last)) stop('length(na.last) = 0')
   if (length(na.last) != 1L) {
@@ -48,7 +48,7 @@ frankv = function(x, cols=seq_along(x), order=1L, na.last=TRUE, ties.method=c("a
     xorder  = seq_along(x[[1L]])
   }
   ans = switch(ties.method,
-    average = , min = , max =, dense = {
+    average = , min = , max =, dense =, last = {
       rank = .Call(Cfrank, xorder, xstart, uniqlengths(xstart, length(xorder)), ties.method)
     },
     first = , random = {
@@ -65,7 +65,7 @@ frankv = function(x, cols=seq_along(x), order=1L, na.last=TRUE, ties.method=c("a
   ans
 }
 
-frank = function(x, ..., na.last=TRUE, ties.method=c("average", "first", "random", "max", "min", "dense")) {
+frank = function(x, ..., na.last=TRUE, ties.method=c("average", "first", "last", "random", "max", "min", "dense")) {
   cols = substitute(list(...))[-1L]
   if (identical(as.character(cols), "NULL")) {
     cols  = NULL

inst/tests/tests.Rraw

@@ -5480,7 +5480,7 @@ test_no = 1368.0
 for (i in seq_along(dt)) {
   col = dt[[i]]
   for (j in list(TRUE, FALSE, "keep")) {
-    for (k in c("average", "min", "max", "first")) {
+    for (k in c("average", "min", "max", "first", "last")) {
       if (k == "random") set.seed(45L)
       if (class(col) == "integer64") {
         r1 = rank(as.integer(col), ties.method=k, na.last=j)
@@ -5511,7 +5511,7 @@ if (test_bit64) dt[, DD := as.integer64(DD)]
 test_no = 1369.0
 for (i in seq_along(dt)) {
   col = dt[[i]]
-  for (k in c("average", "min", "max", "first")) {
+  for (k in c("average", "min", "max", "first", "last")) {
     if (k == "random") set.seed(45L)
     if (class(col) == "integer64") {
       r1 = rank(as.integer(col), ties.method=k, na.last=NA)

man/frank.Rd

@@ -4,19 +4,19 @@
 \alias{rank}
 \title{Fast rank}
 \description{
-  Similar to \code{base::rank} but \emph{much faster}. And it accepts vectors, lists, data.frames or data.tables as input. In addition to the \code{ties.method} possibilities provided by \code{base::rank}, it also provides \code{ties.method="dense"}.
-  
+  Similar to \code{base::rank} but \emph{much faster}. And it accepts vectors, lists, \code{data.frame}s or \code{data.table}s as input. In addition to the \code{ties.method} possibilities provided by \code{base::rank}, it also provides \code{ties.method="dense"}.
+
   Like \code{\link{forder}}, sorting is done in "C-locale"; in particular, this may affect how capital/lowercase letters are ranked. See Details on \code{forder} for more.
 
   \code{bit64::integer64} type is also supported.
 }
 
 \usage{
 frank(x, \dots, na.last=TRUE, ties.method=c("average",
-  "first", "random", "max", "min", "dense"))
+  "first", "last", "random", "max", "min", "dense"))
 
 frankv(x, cols=seq_along(x), order=1L, na.last=TRUE,
-      ties.method=c("average", "first", "random",
+      ties.method=c("average", "first", "last", "random",
         "max", "min", "dense"))
 
 }
@@ -33,7 +33,7 @@ frankv(x, cols=seq_along(x), order=1L, na.last=TRUE,
 
   \code{frank} is not limited to vectors. It accepts \code{data.table}s (and \code{list}s and \code{data.frame}s) as well. It accepts unquoted column names (with names preceded with a \code{-} sign for descending order, even on character vectors), for e.g., \code{frank(DT, a, -b, c, ties.method="first")} where \code{a,b,c} are columns in \code{DT}. The equivalent in \code{frankv} is the \code{order} argument.
 
-  In addition to the \code{ties.method} values possible using base's \code{\link[base]{rank}}, it also provides another additional argument \emph{"dense"} which returns the ranks without any gaps in the ranking. See examples.
+  In addition to the \code{ties.method} values possible using base's \code{\link[base]{rank}}, it also provides another additional argument \code{"dense"} which returns the ranks without any gaps in the ranking. See examples.
 }
 \value{
   A numeric vector of length equal to \code{NROW(x)} (unless \code{na.last = NA}, when missing values are removed). The vector is of integer type unless \code{ties.method = "average"} when it is of double type (irrespective of ties).

src/frank.c

@@ -69,14 +69,16 @@ SEXP dt_na(SEXP x, SEXP cols) {
 
 SEXP frank(SEXP xorderArg, SEXP xstartArg, SEXP xlenArg, SEXP ties_method) {
   const int *xstart = INTEGER(xstartArg), *xlen = INTEGER(xlenArg), *xorder = INTEGER(xorderArg);
-  enum {MEAN, MAX, MIN, DENSE, SEQUENCE} ties = MEAN; // RUNLENGTH
+  enum {MEAN, MAX, MIN, DENSE, SEQUENCE, LAST} ties; // RUNLENGTH
 
-  if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "average"))  ties = MEAN;
-  else if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "max")) ties = MAX;
-  else if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "min")) ties = MIN;
-  else if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "dense")) ties = DENSE;
-  else if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "sequence")) ties = SEQUENCE;
-  // else if (!strcmp(CHAR(STRING_ELT(ties_method, 0)), "runlength")) ties = RUNLENGTH;
+  const char *pties = CHAR(STRING_ELT(ties_method, 0));
+  if (!strcmp(pties, "average"))  ties = MEAN;
+  else if (!strcmp(pties, "max")) ties = MAX;
+  else if (!strcmp(pties, "min")) ties = MIN;
+  else if (!strcmp(pties, "dense")) ties = DENSE;
+  else if (!strcmp(pties, "sequence")) ties = SEQUENCE;
+  else if (!strcmp(pties, "last")) ties = LAST;
+  // else if (!strcmp(pties, "runlength")) ties = RUNLENGTH;
   else error(_("Internal error: invalid ties.method for frankv(), should have been caught before. please report to data.table issue tracker")); // # nocov
   const int n = length(xorderArg);
   SEXP ans = PROTECT(allocVector(ties==MEAN ? REALSXP : INTSXP, n));
@@ -118,6 +120,15 @@ SEXP frank(SEXP xorderArg, SEXP xstartArg, SEXP xlenArg, SEXP ties_method) {
           ians[xorder[j]-1] = k++;
       }
       break;
+    case LAST :
+      for (int i=0; i<length(xstartArg); ++i) {
+        // alternatively, also loop k from xstart[i]+xlen[i]-1 and decrement
+        int offset = 2*xstart[i]+xlen[i]-2;
+        for (int j=xstart[i]-1; j<xstart[i]+xlen[i]-1; ++j) {
+          ians[xorder[j]-1] = offset-j;
+        }
+      }
+      break;
     // case RUNLENGTH :
     //   for (i = 0; i < length(xstartArg); i++) {
     //     k=1;