Abstract

We present important changes in the development version of R (referred to as R-devel, to become R 4.3). Some statistics on bug tracking activities in 2022 are also provided.

R-devel selected changes

R 4.3.0 is due to be released around April 2023. The following gives a selection of the most important changes in R-devel, which are likely to appear in the new release.

Dates and times

There are a number of (robustness) improvements in the handling of dates and times. These include warnings about extrapolation for datetimes before 1902/1900, finer control for padding when printing years, improved detection of offset with strftime() (%z), inclusion of system time zone and information on timezone support implementation in sessionInfo(), more robust handling of hand-crafted POSIXlt objects, optional support for using system timezone support on recent macOS, improved detection of the system time zone on Windows and improved default tick locations and default formats in axis.Date() and axis.POSIXct().

Encoding support

Performance of regular expression operations in R has been improved by reducing the costs of encoding conversions. With perl=FALSE, all inputs have to be converted to UTF-16 or UTF-32, and the conversion is now faster. With perl=TRUE, performance has been improved by opting out from duplicate checks for UTF-8 validity in PCRE2. With fixed=TRUE, performance has been improved by taking advantage of the properties of UTF-8. One of the motivations for the speedups was to reduce the incentive for using useBytes=TRUE with regular expression operations, which often leads to incorrect results or errors due to producing invalid strings.

See Speedups in operations with regular expressions for more information.
The support for encoding-agnostic string operations in R using the “bytes” encoding has been improved. It is now possible to read a text file directly as bytes. Regexp operations, when creating new strings by splitting or substituting, now also flag them as “bytes” when any of the input has been flagged as such. This simplifies encoding-agnostic parsing of files such as DESCRIPTION. iconv(,from="") now respects the encoding flag of the input string, making it easier to recover from type-instability in return values of regular expression operations. Improving the support for encoding-agnostic operations using the “bytes” encoding comes together with stricter checking of validity of real strings in a character encoding, e.g. “unknown/native”, which has been helpful in revealing user errors. In the long term, it should also help to simplify encoding support in R.

See Improvements in handling bytes encoding for more information. The blog includes a detailed introduction to string and encoding support in R.

See Why to avoid \x in regular expressions for related information on the danger of using \x escapes in regular expressions, which leads to errors, that are now more likely to be detected by R. This is closely related as \x is a common way to create invalid strings.

Graphics

The grDevices and grid packages have new functions for rendering typeset glyphs, primarily: grDevices::glyphInfo() and grid::grid.glyph().
The behaviour of compositing operators in grid::grid.group() has been tweaked to allow consistency across graphics devices.
The grDevices::quartz() device will support gradient fills, pattern fills, clipping paths, masks, compositing operators, affine transformations, stroked/filled paths, and glyphs. To be soon merged to R-devel.

Accessibility on Windows

Rgui console on Windows now works better with the open-source NVDA screen reader when the “full” blinking cursor is selected. This is due to improved implementation of the console cursor (when it is displayed and hidden with respect to application startup and window focus) on which makes it easier for the screen reader to detect where the cursor is. Previously, NVDA was not able to read out the character under the cursor moved by the arrow keys.
The drop-field GraphApp control, which is used in the Rgui configuration editor, has been extended so that it can be left by pressing the TAB key, so without using the mouse.
GraphApp has been extended to allow reverse-order navigation through the controls using Shift+TAB key, which can now be done also in the Rgui configuration editor.

Other selected changes

Using vectors of more than one element with the logical operators && and || will give an error in R 4.3.0 (a warning in R 4.2.x, a check error since R 3.6.0).
Support for working with concordances has been extended from Sweave to help files. A concordance is a mapping between lines in an intermediate file (e.g., .tex or .html) and lines in the corresponding input file (e.g., .Rnw or .Rd), which, for example, allows relating problems in the intermediate file to the source file from which it was generated.

See Concordances for more information.
The implementation of the sampling profiler, Rprof(), has been improved. On macOS, the profiler is now more robust against high load on the system by using low-level Mach API to avoid a race condition between initialization of pthread data and arrival of a profiler signal. This race condition could lead to a live-lock when the system has been overloaded due to a too short profiling interval. As an additional measure, Rprof() now refuses to use a too short profiling interval, which in the first place would lead to incorrect profiling results. To prevent a deadlock seen on Windows, the profiler has been rewritten to avoid using C runtime functions while the main thread is suspended.
Package installation now uses C++17 as the default C++ standard (and there is initial support for C++23). Also, there now is support for a package to indicate the version of the C standard which should be used to compile it, and for the installing user to specify this. In most cases, C17 (a “bug-fix” of C11) is used by default.
Producing PDF manuals (R CMD Rd2pdf) now loads standard AMS-LaTeX packages for greater coverage of math commands in Rd equations (e.g., \lVert and \text), and for consistency with the enhanced HTML math rendering introduced in R 4.2.0. This change has been backported to the R 4.2 release branch.
The "repos" option is now initialized from the repositories file, see ?R_REPOSITORIES, allowing the default CRAN mirror to be set therein.

Changes in R

Tomas Kalibera

Sebastian Meyer

Kurt Hornik

2022-12-01