various coverage (#3757)

NEWS.md

@@ -258,6 +258,8 @@
 
 14. The warning message when using `keyby=` together with `:=` is clearer, [#2763](https://github.com/Rdatatable/data.table/issues/2763). Thanks to @eliocamp.
 
+15. `first` and `last` gain an explicit `n=1L` argument so that it's clear the default is 1, and their almost identical manual pages have been merged into one.
+
 
 ### Changes in [v1.12.2](https://github.com/Rdatatable/data.table/milestone/14?closed=1)  (07 Apr 2019)
 

R/last.R

@@ -3,35 +3,35 @@
 # This last is implemented this way for compatibility with xts::last which is S3 generic taking 'n' and 'keep' arguments
 # We'd like last() on vectors to be fast, so that's a direct x[NROW(x)] as it was in data.table, otherwise use xts's.
 # If xts is loaded higher than data.table, xts::last will work but slower.
-last = function(x, ...) {
+last = function(x, n=1L, ...) {
   if (nargs()==1L) {
     if (is.vector(x)) {
       if (!length(x)) return(x) else return(x[[length(x)]])  # for vectors, [[ works like [
     } else if (is.data.frame(x)) return(x[NROW(x),])
   }
   if(!requireNamespace("xts", quietly = TRUE)) {
-    tail(x, n = 1L, ...) # nocov
+    tail(x, n=n, ...) # nocov
   } else {
     # fix with suggestion from Joshua, #1347
     if (!"package:xts" %chin% search()) {
-      tail(x, n = 1L, ...) # nocov
-    } else xts::last(x, ...) # UseMethod("last") doesn't find xts's methods, not sure what I did wrong.
+      tail(x, n=n, ...) # nocov
+    } else xts::last(x, n=n, ...) # UseMethod("last") doesn't find xts's methods, not sure what I did wrong.
   }
 }
 
 # first(), similar to last(), not sure why this wasn't exported in the first place...
-first = function(x, ...) {
+first = function(x, n=1L, ...) {
   if (nargs()==1L) {
     if (is.vector(x)) {
       if (!length(x)) return(x) else return(x[[1L]])
     } else if (is.data.frame(x)) return(x[1L,])
   }
   if(!requireNamespace("xts", quietly = TRUE)) {
-    head(x, n = 1L, ...) # nocov
+    head(x, n=n, ...) # nocov
   } else {
     # fix with suggestion from Joshua, #1347
     if (!"package:xts" %chin% search()) {
-      head(x, n = 1L, ...) # nocov
-    } else xts::first(x, ...) # nocov
+      head(x, n=n, ...) # nocov
+    } else xts::first(x, n=n, ...) # nocov
   }
 }

R/test.data.table.R

@@ -58,7 +58,7 @@ test.data.table = function(verbose=FALSE, pkg="pkg", silent=FALSE, with.other.pa
   # Sys.setlocale("LC_CTYPE", "")   # just for CRAN's Mac to get it off C locale (post to r-devel on 16 Jul 2012)
 
   cat("getDTthreads(verbose=TRUE):\n")         # for tracing on CRAN; output to log before anything is attempted
-  print(getDTthreads(verbose=TRUE))            # print output of getDTthreads() verbatim as simply as possible; e.g. without depending on data.table for formatting
+  print(invisible(getDTthreads(verbose=TRUE))) # print output of getDTthreads() verbatim as simply as possible; e.g. without depending on data.table for formatting
   cat("test.data.table() running:", fn, "\n")  # print fn to log before attempting anything on it (in case it is missing); on same line for slightly easier grep
   env = new.env(parent=.GlobalEnv)
   assign("testDir", function(x) file.path(fulldir, x), envir=env)

R/transpose.R

@@ -2,9 +2,10 @@ transpose = function(l, fill=NA, ignore.empty=FALSE, keep.names=NULL, make.names
   if (!is.null(make.names)) {
     stopifnot(length(make.names)==1L)
     if (is.character(make.names)) {
-      make.names=chmatch(make.names, names(l))
-      if (is.na(make.names))
+      m = chmatch(make.names, names(l))
+      if (is.na(m))
         stop("make.names='",make.names,"' not found in names of input")
+      make.names = m
     } else {
       make.names = as.integer(make.names)
       if (is.na(make.names) || make.names<1L || make.names>length(l))

inst/tests/tests.Rraw

@@ -7778,6 +7778,7 @@ test(1571.3, names(tstrsplit(X$a, "", fixed=TRUE, names=letters[1:4])), letters[
 test(1571.4, tstrsplit(X$a, "", fixed=TRUE, keep=c(2,4)), list(c("B", "E"), c(NA, "G")))
 test(1571.5, tstrsplit(X$a, "", fixed=TRUE, keep=c(2,7)), error="should contain integer")
 test(1571.6, tstrsplit(X$a, "", fixed=TRUE, keep=c(2,4), names=letters[1:5]), error="is not equal to")
+test(1571.7, tstrsplit(X$a, "", fixed=TRUE, names=1), error="'names' must be TRUE/FALSE or a character vector")
 
 # fix for #1367, quote="" argument in use. Using embedded quotes in the example below reads the
 # first two columns as one. I couldn't find a way to avoid introducing quote argument.
@@ -9895,6 +9896,7 @@ test(1686.2, DT[, .(V1=A,B)], DT[, c(.(get("A")), .SD), .SDcols="B"])
 test(1687.1, first(1:5), 1L)
 test(1687.2, first(data.table(x=1:5, y=6:10)), data.table(x=1L, y=6L))
 test(1687.3, first(integer(0L)), integer(0L))
+test(1687.4, first(1:5, 2), 1:2)
 
 if (test_bit64) {
   # fix for #1385 and part of #1459
@@ -15510,17 +15512,18 @@ test(2072.067, fifelse(c(TRUE, NA, TRUE, FALSE, FALSE, FALSE), factor(NA), facto
                factor(c(NA,NA,NA,NA,NA,NA)))
 
 DT = data.table(x=1:5, y=6:10)
-test(2073.1, transpose(DT, keep.names="rn"),
+test(2073.01, transpose(DT, keep.names="rn"),
              ans<-data.table(rn=c('x','y'), V1=c(1L, 6L), V2=c(2L, 7L), V3=c(3L, 8L), V4=c(4L, 9L), V5=c(5L, 10L)))
-test(2073.2, transpose(DT, keep.names=TRUE), error="either NULL.*name of the first column of the result")
-test(2073.3, transpose(ans, make.names="rn"), DT)
-test(2073.4, transpose(ans, keep.names="rn", make.names="rn"), data.table(rn=paste0("V",1:5), x=1:5, y=6:10))
+test(2073.02, transpose(DT, keep.names=TRUE), error="either NULL.*name of the first column of the result")
+test(2073.03, transpose(ans, make.names="rn"), DT)
+test(2073.04, transpose(ans, make.names="notthere"), error="make.names='notthere' not found in names of input")
+test(2073.05, transpose(ans, keep.names="rn", make.names="rn"), data.table(rn=paste0("V",1:5), x=1:5, y=6:10))
 L = list(a=1:3, rn=LETTERS[1:3], b=4:6)
-test(2073.5, transpose(L, make.names=0),  error="make.names=0 is out of range [1,ncol=3]")
-test(2073.6, transpose(L, make.names=4),  error="make.names=4 is out of range [1,ncol=3]")
-test(2073.7, transpose(L, make.names=NA), error="make.names=NA is out of range [1,ncol=3]")
-test(2073.8, transpose(L, make.names=2), list(A=INT(1,4), B=INT(2,5), C=INT(3,6)))
-test(2073.9, transpose(L, make.names=2, keep.names='foo'), list(foo=c("a","b"), A=INT(1,4), B=INT(2,5), C=INT(3,6)))
+test(2073.06, transpose(L, make.names=0),  error="make.names=0 is out of range [1,ncol=3]")
+test(2073.07, transpose(L, make.names=4),  error="make.names=4 is out of range [1,ncol=3]")
+test(2073.08, transpose(L, make.names=NA), error="make.names=NA is out of range [1,ncol=3]")
+test(2073.09, transpose(L, make.names=2), list(A=INT(1,4), B=INT(2,5), C=INT(3,6)))
+test(2073.10, transpose(L, make.names=2, keep.names='foo'), list(foo=c("a","b"), A=INT(1,4), B=INT(2,5), C=INT(3,6)))
 
 
 ###################################

man/last.Rd

@@ -1,34 +1,36 @@
 \name{last}
+\alias{first}
 \alias{last}
-\title{ Last item of an object }
+\title{ First/last item of an object }
 \description{
-Returns the last item of a vector or list, or the last row of a data.frame or
-data.table.
+Returns the first/last item of a vector or list, or the first/last row of a data.frame
+or data.table. The main difference to head/tail is that the default for \code{n} is 1
+rather than 6.
 }
 \usage{
-last(x, \dots)
+first(x, n=1L, \dots)
+last(x, n=1L, \dots)
 }
 \arguments{
-\item{x}{ A vector, list, data.frame or data.table. Otherwise the S3 method of
-\code{xts::last} is deployed. }
-\item{\dots}{ Not applicable for \code{data.table::last}. Any arguments here are
-passed through to \code{xts::last}. }
+\item{x}{ A vector, list, data.frame or data.table. Otherwise the S3 method
+of \code{xts::first} is deployed. }
+\item{n}{ A numeric vector length 1. How many items to select. }
+\item{\dots}{ Not applicable for \code{data.table} first/last. Any arguments here
+are passed through to \code{xts}'s first/last. }
 }
-% \details{
-% }
 \value{
-If no other arguments are supplied it depends on the type of x. The last item
-of a vector or list. The last row of a \code{data.frame} or \code{data.table}.
-Otherwise, whatever \code{xts::last} returns (if package xts has been loaded,
-otherwise a helpful error).
-
-If any argument is supplied in addition to \code{x} (such as \code{n} or
-\code{keep} in \code{xts::last}), regardless of \code{x}'s type, then
-\code{xts::last} is called if xts has been loaded, otherwise a helpful error.
+If no other arguments are supplied it depends on the type of \code{x}. The first/last item
+of a vector or list. The first/last row of a \code{data.frame} or \code{data.table}.
+For other types, or if any argument is supplied in addition to \code{x} (such as \code{n}, or
+\code{keep} in \code{xts}) regardless of \code{x}'s type, then \code{xts::first}/
+\code{xts::last} is called if \code{xts} has been loaded, otherwise \code{utils::head}/\code{utils::tail}.
 }
-\seealso{ \code{\link{NROW}}, \code{\link{head}}, \code{\link{tail}},
-\code{\link{first}} }
+\seealso{ \code{\link{NROW}}, \code{\link{head}}, \code{\link{tail}} }
 \examples{
+first(1:5) # [1] 1
+x = data.table(x=1:5, y=6:10)
+first(x) # same as x[1]
+
 last(1:5) # [1] 5
 x = data.table(x=1:5, y=6:10)
 last(x) # same as x[5]