NEWS | R Documentation

## R News

### CHANGES IN R 4.0.3

#### NEW FEATURES

- On platforms using `configure` option --with-internal-tzcode, additional values `"internal"` and (on macOS only) `"macOS"` are accepted for the environment variable TZDIR. (See `?TZDIR`.)

  On macOS, `"macOS"` is used by default if the system timezone database is a newer version than that in the R installation.

- When `install.packages(type = "source")` fails to find a package in a repository it mentions package versions which are excluded by their R version requirement and links to hints on why a package might not be found.

- The default value for `options("timeout")` can be set from enviromnent variable R_DEFAULT_INTERNET_TIMEOUT, still defaulting to 60 (seconds) if that is not set or invalid.

  This may be needed when child R processes are doing downloads, for example during the installation of source packages which download jars or other forms of data.

#### LINK-TIME OPTIMIZATION on a UNIX-ALIKE

- There is now support for parallelized Link-Time Optimization (LTO) with GCC and for ‘thin’ LTO with `clang` via setting the LTO macro.

- There is support for setting a different LTO flag for the Fortran compiler, including to empty when mixing `clang` and `gfortran` (as on macOS). See file ‘config.site’.

- There is a new LTO_LD macro to set linker options for LTO compilation, for example to select an alternative linker or to parallelize thin LTO.

#### DEPRECATED AND DEFUNCT

- The `LINPACK` argument to `chol.default()`, `chol2inv()`, `solve.default()` and `svd()` has been defunct since R 3.1.0. Using it now gives a warning which will become an error in R 4.1.0.

#### BUG FIXES

- The code mitigating stack overflow with PCRE regexps on very long strings is enabled for PCRE2 < 10.30 also when JIT is enabled, since stack overflows have been seen in that case.

- Fix to correctly show the group labels in `dotchart()` (which where lost in the `ylab` improvement for R 4.0.0).

- `addmargins(*, ..)` now also works when `fn()` is a local function, thanks to bug report and patch PR#17124 from Alex Bertram.

- `rank(x)` and hence `sort(x)` now work when `x` is an object (as per `is.object(x)`) of type `"raw"` and provides a valid ``[`` method, e.g., for `gmp::as.bigz(.)` numbers.

- `chisq.test(*, simulate.p.value=TRUE)` and `r2dtable()` now work correctly for large table entries (in the millions). Reported by Sebastian Meyer and investigated by more helpers in PR#16184.

- Low-level socket read/write operations have been fixed to correctly signal communication errors. Previously, such errors could lead to a segfault due to invalid memory access. Reported and debugged by Dmitriy Selivanov in PR#17850.

- `quantile(x, pr)` works more consistently for `pr` values slightly outside [0,1], thanks to Suharto Anggono's PR#17891.

  Further, `quantile(x, prN, names=FALSE)` now works even when `prN` contains `NA`s, thanks to Anggono's PR#17892. Ditto for ordered factors or `Date` objects when `type = 1` or `3`, thanks to PR#17899.

- Libcurl-based internet access, including `curlGetHeaders()`, was not respecting the `"timeout"` option. If this causes unanticipated timeouts, consider increasing the default by setting R_DEFAULT_INTERNET_TIMEOUT.

- `as.Date(<char>)` now also works with an initial `""`, thanks to Michael Chirico's PR#17909.

- `isS3stdGeneric(f)` now detects an S3 generic also when it it is `trace()`d, thanks to Gabe Becker's PR#17917.

- `R_allocLD()` has been fixed to return memory aligned for long double type PR#16534.

- `fisher.test()` no longer segfaults when called again after its internal stack has been exceeded PR#17904.

- Accessing a long vector represented by a compact integer sequence no longer segfaults (reported and debugged by Hugh Parsonage).

- `duplicated()` now works also for strings with multiple encodings inside a single vector PR#17809.

- `phyper(11, 15, 0, 12, log.p=TRUE)` no longer gives `NaN`; reported as PR#17271 by Alexey Stukalov.

- Fix incorrect calculation in `logLik.nls()` PR#16100, patch from Sebastian Meyer.

- A very old bug could cause a segfault in `model.matrix()` when terms involved logical variables. Part of PR#17879.

- `model.frame.default()` allowed `data = 1`, leading to involuntary variable capture (rest of PR#17879).

- `tar()` no longer skips non-directory files, thanks to a patch by Sebastian Meyer, fixing the remaining part of PR#16716.

### CHANGES IN R 4.0.2

#### UTILITIES

- `R CMD check` skips vignette re-building (with a warning) if the VignetteBuilder package(s) are not available.

#### BUG FIXES

- Paths with non-ASCII characters caused problems for package loading on Windows PR#17833.

- Using tcltk widgets no longer crashes R on Windows.

- `source(*, echo=TRUE)` no longer fails in some cases with empty lines; reported by Bill Dunlap in PR#17769.

- `on.exit()` now correctly matches named arguments, thanks to PR#17815 (including patch) by Brodie Gaslam.

- `regexpr(*, perl=TRUE)` no longer returns incorrect positions into text containing characters outside of the Unicode Basic Multilingual Plane on Windows.

### CHANGES IN R 4.0.1

#### NEW FEATURES

- `paste()` and `paste0()` gain a new optional argument `recycle0`. When set to true, zero-length arguments are recycled leading to `character(0)` after the `sep`-concatenation, i.e., to the empty string `""` if `collapse` is a string and to the zero-length value `character(0)` when `collapse = NULL`.

  A package whose code uses this should depend on R (>= 4.0.1).

- The `summary(<warnings>)` method now maps the counts correctly to the warning messages.

#### BUG FIXES

- `aov(frml, ...)` now also works where the `formula` deparses to more than 500 characters, thanks to a report and patch proposal by Jan Hauffa.

- Fix a dozen places (code, examples) as `Sys.setlocale()` returns the new rather than the previous setting.

- Fix for adding two complex grid units via `sum()`. Thanks to Gu Zuguang for the report and Thomas Lin Pedersen for the patch.

- Fix `parallel::mclapply(..., mc.preschedule=FALSE)` to handle raw vector results correctly. PR#17779

- Computing the `base` value, i.e., 2, “everywhere”, now uses `FLT_RADIX`, as the original ‘machar’ code looped indefinitely on the ppc64 architecture for the `longdouble` case.

- In R 4.0.0, `sort.list(x)` when `is.object(x)` was true, e.g., for `x <- I(letters)`, was accidentally using `method = "radix"`. Consequently, e.g., `merge(<data.frame>)` was much slower than previously; reported in PR#17794.

- `plot(y ~ x, ylab = quote(y[i]))` now works, as e.g., for `xlab`; related to PR#10525.

- `parallel::detect.cores(all.tests = TRUE)` tries a matching OS name before the other tests (which were intended only for unknown OSes).

- Parse data for raw strings is now recorded correctly. Reported by Gabor Csardi.

### CHANGES IN R 4.0.0

#### SIGNIFICANT USER-VISIBLE CHANGES

- Packages need to be (re-)installed under this version (4.0.0) of R.

- `matrix` objects now also inherit from class `"array"`, so e.g., `class(diag(1))` is `c("matrix", "array")`. This invalidates code incorrectly assuming that `class(matrix_obj))` has length one.

  S3 methods for class `"array"` are now dispatched for `matrix` objects.

- There is a new syntax for specifying raw character constants similar to the one used in C++: `r"(...)"` with `...` any character sequence not containing the sequence )". This makes it easier to write strings that contain backslashes or both single and double quotes. For more details see `?Quotes`.

- R now uses a stringsAsFactors = FALSE default, and hence by default no longer converts strings to factors in calls to `data.frame()` and `read.table()`.

  A large number of packages relied on the previous behaviour and so have needed/will need updating.

- The `plot()` S3 generic function is now in package base rather than package graphics, as it is reasonable to have methods that do not use the graphics package. The generic is currently re-exported from the graphics namespace to allow packages importing it from there to continue working, but this may change in future.

  Packages which define S4 generics for `plot()` should be re-installed and package code using such generics from other packages needs to ensure that they are imported rather than rely on their being looked for on the search path (as in a namespace, the base namespace has precedence over the search path).

#### REFERENCE COUNTING

- Reference counting is now used instead of the `NAMED` mechanism for determining when objects can be safely mutated in base C code. This reduces the need for copying in some cases and should allow further optimizations in the future. It should help make the internal code easier to maintain.

  This change is expected to have almost no impact on packages using supported coding practices in their C/C++ code.

#### MIGRATION TO PCRE2

- This version of R is built against the PCRE2 library for Perl-like regular expressions, if available. (On non-Windows platforms PCRE1 can optionally be used if PCRE2 is not available at build time.) The version of PCRE in use can be obtained via `extSoftVersion()`: PCRE1 (formerly known as ‘PCRE’) has versions <= 8, PCRE2 versions >= 10.

- Making PCRE2 available when building R from source is strongly recommended (preferably version 10.30 or later) as PCRE1 is no longer developed: version 8.44 is ‘likely to be the final release’.

- PCRE2 reports errors for some regular expressions that were accepted by PCRE1. A hyphen now has to be escaped in a character class to be interpreted as a literal (unless first or last in the class definition). \R, \B and \X are no longer allowed in character classes (PCRE1 treated these as literals).

- Option `PCRE_study` is no longer used with PCRE2, and is reported as `FALSE` when that is in use.

#### NEW FEATURES

- `assertError()` and `assertWarning()` (in package tools) can now check for specific error or warning classes via the new optional second argument `classes` (which is not back compatible with previous use of an unnamed second argument).

- `DF2formula()`, the utility for the data frame method of `formula()`, now works without parsing and explicit evaluation, starting from Suharto Anggono's suggestion in PR#17555.

- `approxfun()` and `approx()` gain a new argument `na.rm` defaulting to true. If set to false, missing `y` values now propagate into the interpolated values.

- Long vectors are now supported as the `seq` argument of a `for()` loop.

- `str(x)` gets a new `deparse.lines` option with a default to speed it up when `x` is a large `call` object.

- The internal traceback object produced when an error is signalled (`.Traceback`), now contains the `call`s rather than the `deparse()`d calls, deferring the deparsing to the user-level functions `.traceback()` and `traceback()`. This fulfils the wish of PR#17580, reported including two patch proposals by Brodie Gaslam.

- `data.matrix()` now converts character columns to factors and from this to integers.

- `package.skeleton()` now explicitly lists all exports in the ‘NAMESPACE’ file.

- New function `.S3method()` to register S3 methods in R scripts.

- `file.path()` has some support for file paths not in the session encoding, e.g. with UTF-8 inputs in a non-UTF-8 locale the output is marked as UTF-8.

- Most functions with file-path inputs will give an explicit error if a file-path input in a marked encoding cannot be translated (to the native encoding or in some cases on Windows to UTF-8), rather than translate to a different file path using escapes. Some (such as `dir.exists()`, `file.exists()`, `file.access()`, `file.info()`, `list.files()`, `normalizePath()` and `path.expand()`) treat this like any other non-existent file, often with a warning.

- There is a new help document accessed by `help("file path encoding")` detailing how file paths with marked encodings are handled.

- New function `list2DF()` for creating data frames from lists of variables.

- `iconv()` has a new option `sub = "Unicode"` to translate UTF-8 input invalid in the to encoding using <U+xxxx> escapes.

- There is a new function `infoRDS()` providing information about the serialization format of a serialized object.

- S3 method lookup now by default skips the elements of the search path between the global and base environments.

- Added an argument `add_datalist(*, small.size = 0)` to allow the creation of a ‘data/datalist’ file even when the total size of the data sets is small.

- The backquote function `bquote()` has a new argument `splice` to enable splicing a computed list of values into an expression, like `,@` in LISP's backquote.

- The formula interface to `t.test()` and `wilcox.test()` has been extended to handle one-sample and paired tests.

- The `palette()` function has a new default set of colours (which are less saturated and have better accessibility properties). There are also some new built-in palettes, which are listed by the new `palette.pals()` function. These include the old default palette under the name `"R3"`. Finally, the new `palette.colors()` function allows a subset of colours to be selected from any of the built-in palettes.

- `n2mfrow()` gains an option `asp = 1` to specify the aspect ratio, fulfilling the wish and extending the proposal of Michael Chirico in PR#17648.

- For `head(x, n)` and `tail()` the default and other S3 methods notably for vector `n`, e.g. to get a “corner” of a matrix, has been extended to `array`'s of higher dimension thanks to the patch proposal by Gabe Becker in PR#17652. Consequently, optional argument `addrownums` is deprecated and replaced by the (more general) argument `keepnums`. An invalid second argument `n` now leads to typically more easily readable error messages.

- New function `.class2()` provides the full character vector of class names used for S3 method dispatch.

- Printing `methods(..)` now uses a new `format()` method.

- `sort.list(x)` now works for non-atomic objects `x` and `method = "auto"` (the default) or `"radix"` in cases `order(x)` works, typically via a `xtfrm()` method.

- Where they are available, `writeBin()` allows long vectors.

- New function `deparse1()` produces one string, wrapping `deparse()`, to be used typically in `deparse1(substitute(*))`, e.g., to fix PR#17671.

- `wilcox.test()` enhancements: In the (non-paired) two-sample case, `Inf` values are treated as very large for robustness consistency. If exact computations are used, the result now has `"exact"` in the `method` element of its return value. New arguments `tol.root` and `digits.rank` where the latter may be used for stability to treat very close numbers as ties.

- `readBin()` and `writeBin()` now report an error for an invalid `endian` value. The affected code needs to be fixed with care as the old undocumented behavior was to swap endian-ness in such cases.

- `sequence()` is now an S3 generic with an internally implemented default method, and gains arguments to generate more complex sequences. Based on code from the S4Vectors Bioconductor package and the advice of Hervé Pagès.

- `print()`'s default method and many other methods (by calling the default eventually and passing `...`) now make use of a new optional `width` argument, avoiding the need for the user to set and reset `options("width")`.

- `memDecompress()` supports the RFC 1952 format (e.g. in-memory copies of `gzip`-compressed files) as well as RFC 1950.

- `memCompress()` and `memDecompress()` support long raw vectors for types `"gzip"` and `"zx"`.

- `sweep()` and `slice.index()` can now use names of dimnames for their `MARGIN` argument (`apply` has had this for almost a decade).

- New function `proportions()` and `marginSums()`. These should replace the unfortunately named `prop.table()` and `margin.table()`. They are drop-in replacements, but also add named-margin functionality. The old function names are retained as aliases for back-compatibility.

- Functions `rbinom()`, `rgeom()`, `rhyper()`, `rpois()`, `rnbinom(),` `rsignrank()` and `rwilcox()` which have returned integer since R 3.0.0 and hence `NA` when the numbers would have been outside the integer range, now return double vectors (without NAs, typically) in these cases.

- `matplot(x,y)` (and hence `matlines()` and `matpoints()`) now call the corresponding methods of `plot()` and `lines()`, e.g, when `x` is a `"Date"` or `"POSIXct"` object; prompted by Spencer Graves' suggestion.

- `stopifnot()` now allows customizing error messages via argument names, thanks to a patch proposal by Neal Fultz in PR#17688.

- `unlink()` gains a new argument `expand` to disable wildcard and tilde expansion. Elements of `x` of value `"~"` are now ignored.

- `mle()` in the `stats4` package has had its interface extended so that arguments to the negative log-likelihood function can be one or more vectors, with similar conventions applying to bounds, start values, and parameter values to be kept fixed. This required a minor extension to class `"mle"`, so saved objects from earlier versions may need to be recomputed.

- The default for `pdf()` is now `useDingbats = FALSE`.

- The default fill colour for `hist()` and `boxplot()` is now `col = "lightgray"`.

- The default order of the levels on the y-axis for `spineplot()` and `cdplot()` has been reversed.

- If the R_ALWAYS_INSTALL_TESTS environment variable is set to a true value, `R CMD INSTALL` behaves as if the --install-tests option is always specified. Thanks to Reinhold Koch for the suggestion.

- New function `R_user_dir()` in package tools suggests paths appropriate for storing R-related user-specific data, configuration and cache files.

- `capabilities()` gains a new logical option `Xchk` to avoid warnings about X11-related capabilities.

- The internal implementation of grid units has changed, but the only visible effects at user-level should be

  - a slightly different print format for some units (especially unit arithmetic),

  - faster performance (for unit operations) and

  - two new functions `unitType()` and `unit.psum()`.

  Based on code contributed by Thomas Lin Pedersen.

- When internal dispatch for `rep.int()` and `rep_len()` fails, there is an attempt to dispatch on the equivalent call to `rep()`.

- Object `.Machine` now contains new `longdouble.*` entries (when R uses long doubles internally).

- `news()` has been enhanced to cover the news on R 3.x and 2.x.

- For consistency, `N <- NULL; N[[1]] <- val` now turns `N` into a `list` also when `val)` has length one. This enables `dimnames(r1)[[1]] <- "R1"` for a 1-row matrix `r1`, fixing PR#17719 reported by Serguei Sokol.

- `deparse(..)`, `dump(..)`, and `dput(x, control = "all")` now include control option `"digits17"` which typically ensures 1:1 invertibility. New option `control = "exact"` ensures numeric exact invertibility via `"hexDigits"`.

- When loading data sets via `read.table()`, `data()` now uses LC_COLLATE=C to ensure locale-independent results for possible string-to-factor conversions.

- A server socket connection, a new connection type representing a listening server socket, is created via `serverSocket()` and can accept multiple socket connections via `socketAccept()`.

- New function `socketTimeout()` changes the connection timeout of a socket connection.

- The time needed to start a homogeneous PSOCK cluster on localhost with many nodes has been significantly reduced (package parallel).

- New `globalCallingHandlers()` function to establish global condition handlers. This allows registering default handlers for specific condition classes. Developed in collaboration with Lionel Henry.

- New function `tryInvokeRestart()` to invoke a specified restart if one is available and return without signaling an error if no such restart is found. Contributed by Lionel Henry in PR#17598.

- `str(x)` now shows the length of `attributes` in some cases for a data frame `x`.

- `Rprof()` gains a new argument `filter.callframes` to request that intervening call frames due to lazy evaluation or explicit `eval()` calls be omitted from the recorded profile data. Contributed by Lionel Henry in PR#17595.

- The handling of `${FOO-bar}` and `${FOO:-bar}` in ‘Renviron’ files now follows POSIX shells (at least on a Unix-alike), so the first treats empty environment variables as set and the second does not. Previously both ignored empty variables. There are several uses of the first form in ‘etc/Renviron’.

- New `classes` argument for `suppressWarnings()` and `suppressMessages()` to selectively suppress only warnings or messages that inherit from particular classes. Based on patch from Lionel Henry submitted with PR#17619.

- New function `activeBindingFunction()` retrieves the function of an active binding.

- New `"cairoFT"` and `"pango"` components in the output of `grSoftVersion()`.

- New argument `symbolfamily` in cairo-based graphics devices and new function `cairoSymbolFont()` that can be used to provide the value for that argument.

#### Windows

- `Rterm` now works also when invoked from MSYS2 terminals. Line editing is possible when command `winpty` is installed.

- `normalizePath()` now resolves symbolic links and normalizes case of long names of path elements in case-insensitive folders (PR#17165).

- `md5sum()` supports UTF-8 file names with characters that cannot be translated to the native encoding (PR#17633).

- `Rterm` gains a new option --workspace to specify the workspace to be restored. This allows equals to be part of the name when opening via Windows file associations (reported by Christian Asseburg).

- `Rterm` now accepts `ALT+xxx` sequences also with NumLock on. Tilde can be pasted with an Italian keyboard (PR#17679).

- R falls back to copying when junction creation fails during package checking (patch from Duncan Murdoch).

#### DEPRECATED AND DEFUNCT

- Make macro F77_VISIBILITY has been removed and replaced by F_VISIBILITY.

- Make macros F77, FCPIFCPLAGS and SHLIB_OPENMP_FCFLAGS have been removed and replaced by FC, FPICFLAGS and SHLIB_OPENMP_FFLAGS respectively. (Most `make` programs will set F77 to the value of FC, which is set for package compilation. But portable code should not rely on this.)

- The deprecated support for specifying C++98 for package installation has been removed.

- `R CMD config` no longer knows about the unused settings F77 and FCPIFCPLAGS, nor CXX98 and similar.

- Either PCRE2 or PCRE1 >= 8.32 (Nov 2012) is required: the deprecated provision for 8.20–8.31 has been removed.

- Defunct functions `mem.limits()`, `.readRDS()`, `.saveRDS()`,.`.find.package()`, and `.path.package()` from package base and `allGenerics()`, `getAccess()`, `getAllMethods()`, `getClassName()`, `getClassPackage()`, `getExtends()`, `getProperties()`, `getPrototype()`, `getSubclasses()`, `getVirtual()`, `mlistMetaName()`, `removeMethodsObject()`, `seemsS4Object()`, `traceOff()`, and `traceOn()` from methods have been removed.

#### C-LEVEL FACILITIES

- `installChar` is now remapped in ‘Rinternals.h’ to `installTrChar`, of which it has been a wrapper since R 3.6.0. Neither are part of the API, but packages using `installChar` can replace it if they depend on R >= 3.6.2.

- Header ‘R_ext/Print.h’ defines R_USE_C99_IN_CXX and hence exposes `Rvprintf` and `REvprintf` if used with a C++11 (or later) compiler.

- There are new Fortran subroutines `dblepr1`, `realpr1` and `intpr1` to print a scalar variable (`gfortran` 10 enforces the distinction between scalars and length-one arrays). Also `labelpr` to print just a label.

- `R_withCallingErrorHandler` is now available for establishing a calling handler in C code for conditions inheriting from class `error`.

#### INSTALLATION on a UNIX-ALIKE

- User-set DEFS (e.g., in ‘config.site’) is now used for compiling packages (including base packages).

- There is a new variant option --enable-lto=check for checking consistency of BLAS/LAPACK/LINPACK calls — see ‘Writing R Extensions’.

- A C++ compiler default is set only if the C++11 standard is supported: it no longer falls back to C++98.

- PCRE2 is used if available. To make use of PCRE1 if PCRE2 is unavailable, configure with option --with-pcre1.

- The minimum required version of `libcurl` is now 7.28.0 (Oct 2012).

- New make target `distcheck` checks

  - R can be rebuilt from the tarball created by `make dist`,

  - the build from the tarball passes `make check-all`,

  - the build installs and uninstalls,

  - the source files are properly cleaned by `make distclean`.

#### UTILITIES

- `R --help` now mentions the option `--no-echo` (renamed from `--slave`) and its previously undocumented short form `-s`.

- `R CMD check` now optionally checks `configure` and `cleanup` scripts for non-Bourne-shell code (‘bashisms’).

- `R CMD check --as-cran` now runs `\donttest` examples (which are run by `example()`) instead of instructing the tester to do so. This can be temporarily circumvented during development by setting environment variable _R_CHECK_DONTTEST_EXAMPLES_ to a false value.

#### PACKAGE INSTALLATION

- There is the beginnings of support for the recently approved C++20 standard, specified analogously to C++14 and C++17. There is currently only limited support for this in compilers, with flags such as -std=c++20 and -std=c++2a. For the time being the `configure` test is of accepting one of these flags and compiling C++17 code.

#### BUG FIXES

- `formula(x)` with `length(x) > 1` character vectors, is deprecated now. Such use has been rare, and has ‘worked’ as expected in some cases only. In other cases, wrong `x` have silently been truncated, not detecting previous errors.

- Long-standing issue where the X11 device could lose events shortly after startup has been addressed (PR#16702).

- The `data.frame` method for `rbind()` no longer drops `<NA>` levels from factor columns by default (PR#17562).

- `available.packages()` and hence `install.packages()` now pass their `...` argument to `download.file()`, fulfilling the wish of PR#17532; subsequently, `available.packages()` gets new argument `quiet`, solving PR#17573.

- `stopifnot()` gets new argument `exprObject` to allow an R object of class `expression` (or other ‘language’) to work more consistently, thanks to suggestions by Suharto Anggono.

- `conformMethod()` now works correctly in cases containing a “`&&` logic” bug, reported by Henrik Bengtsson. It now creates methods with `"missing"` entries in the signature. Consequently, `rematchDefinition()` is amended to use appropriate `.local()` calls with named arguments where needed.

- `format.default(*, scientific = FALSE)` now corresponds to a practically most extreme `options(scipen = n)` setting rather than arbitrary `n = 100`.

- `format(as.symbol("foo"))` now works (returning `"foo"`).

- `postscript(.., title = *)` now signals an error when the title string contains a character which would produce corrupt PostScript, thanks to PR#17607 by Daisuko Ogawa.

- Certain `Ops` (notably comparison such as `==`) now also work for 0-length data frames, after reports by Hilmar Berger.

- `methods(class = class(glm(..)))` now warns more usefully and only once.

- `write.dcf()` no longer mangles field names (PR#17589).

- Primitive replacement functions no longer mutate a referenced first argument when used outside of a complex assignment context.

- A better error message for `contour(*, levels = Inf)`.

- The return value of `contourLines()` is no longer `invisible()`.

- The Fortran code for calculating the `coefficients` component in `lm.influence()` was very inefficient. It has (for now) been replaced with much faster R code (PR#17624).

- `cm.colors(n)` etc no longer append the code for `alpha = 1`, `"FF"`, to all colors. Hence all eight `*.colors()` functions and `rainbow()` behave consistently and have the same non-explicit default (PR#17659).

- `dnorm` had a problematic corner case with `sd == -Inf` or negative `sd` which was not flagged as an error in all cases. Thanks to Stephen D. Weigand for reporting and Wang Jiefei for analyzing this; similar change has been made in `dlnorm()`.

- The optional `iter.smooth` argument of `plot.lm()`, (the `plot()` method for `lm` and `glm` fits) now defaults to `0` for all `glm` fits. Especially for binary observations with high or low fitted probabilities, this effectively deleted all observations of 1 or 0. Also, the type of residuals used in the `glm` case has been switched to `"pearson"` since deviance residuals do not in general have approximately zero mean.

- In `plot.lm`, Cook's distance was computed from unweighted residuals, leading to inconsistencies. Replaced with usual weighted version. (PR#16056)

- Time-series `ts(*, start, end, frequency)` with fractional `frequency` are supported more consistently; thanks to a report from Johann Kleinbub and analysis and patch by Duncan Murdoch in PR#17669.

- In case of errors `mcmapply()` now preserves attributes of returned `"try-error"` objects and avoids simplification, overriding `SIMPLIFY` to `FALSE`. (PR#17653)

- `as.difftime()` gets new optional `tz = "UTC"` argument which should fix behaviour during daylight-savings-changeover days, fixing PR#16764, thanks to proposals and analysis by Johannes Ranke and Kirill Müller.

- `round()` does a better job of rounding “to nearest” by measuring and “to even”; thanks to a careful algorithm originally prompted by the report from Adam Wheeler and then others, in PR#17668.
  `round(x, dig)` for negative digits is much more rational now, notably for large |dig|.

- Inheritance information on S4 classes is maintained more consistently, particularly in the case of class unions (in part due to PR#17596 and a report from Ezra Tucker).

- `is()` behaves more robustly when its argument `class2` is a `classRepresentation` object.

- The warning message when attempting to export an nonexistent class is now more readable; thanks to Thierry Onkelinx for recognizing the problem.

- `choose()` misbehaved in corner cases where it switched `n - k` for `k` and `n` was only nearly integer (report from Erik Scott Wright).

- `mle()` in the `stats4` package had problems combining use of box constraints and fixed starting values (in particular, confidence intervals were affected).

- Operator `?` now has lower precedence than `=` to work as documented, so `=` behaves like `<-` in help expressions (PR#16710).

- `smoothEnds(x)` now returns `integer` type in both cases when `x` is `integer`, thanks to a report and proposal by Bill Dunlap PR#17693.

- The methods package does a better job of tracking inheritance relationships across packages.

- `norm(diag(c(1, NA)), "2")` now works.

- `subset()` had problems with 0-col dataframes (reported by Bill Dunlap, PR#17721).

- Several cases of integer overflow detected by the ‘undefined behaviour sanitizer’ of `clang` 10 have been circumvented. One in `rhyper()` may change the generated value for large input values.

- `dotchart()` now places the y-axis label (`ylab`) much better, not overplotting labels, thanks to a report and suggestion by Alexey Shipunov.

- A rare C-level array overflow in `chull()` has been worked around.

- Some invalid specifications of the day-of-the-year (via `%j`, e.g. day 366 in 2017) or week plus day-of-the-week are now detected by `strptime()`. They now return `NA` but give a warning as they may have given random results or corrupted memory in earlier versions of R.

- `socketConnection(server = FALSE)` now respects the connection timeout also on Linux.

- `socketConnection(server = FALSE)` no longer leaks a connection that is available right away without waiting (e.g. on localhost).

- Socket connections are now robust against spurious readability and spurious availability of an incoming connection.

- `blocking = FALSE` is now respected also on the server side of a socket connection, allowing non-blocking read operations.

- `anova.glm()` and `anova.glmlist()` computed incorrect score (Rao) tests in no-intercept cases. (André Gillibert, PR#17734)

- `summaryRprof()` now should work correctly for the `Rprof(*, memory.profiling=TRUE)` case with small chunk size (and `"tseries"` or similar) thanks to a patch proposal by Benjamin Tyner, in PR#15886.

- `xgettext()` ignores strings passed to `ngettext()`, since the latter is handled by `xngettext()`. Thanks to Daniele Medri for the report and all the recent work he has done on the Italian translations.

- `data(package = "P")` for `P` in base and stats no longer reports the data sets from package datasets (which it did for back compatibility for 16 years), fixing PR#17730.

- `x[[Inf]]` (returning `NULL`) no longer leads to undefined behavior, thanks to a report by Kirill Müller in PR#17756. Further, `x[[-Inf]]` and `x[[-n]]` now give more helpful error messages.

- `Gamma()` family sometimes had trouble storing link name PR#15891

#### BUG FIXES (Windows)

- `Sys.glob()` now supports all characters from the Unicode Basic Multilingual Plane, no longer corrupting some (less commonly used) characters (PR#17638).

- `Rterm` now correctly displays multi-byte-coded characters representable in the current native encoding (at least on Windows 10 they were sometimes omitted, PR#17632).

- `scan()` issues with UTF-8 data when running in a DBCS locale have been resolved (PR#16520, PR#16584).

- `Rterm` now accepts enhanced/arrow keys also with ConPTY.

- R can can now be started via the launcher icon in a user documents directory whose path is not representable in the system encoding.

- `socketConnection(server = FALSE)` now returns instantly also on Windows when connection failure is signalled.

- Problems with UTF-16 surrogate pairs have been fixed in several functions, including `tolower()` and `toupper()` (PR#17645).

### CHANGES in previous versions

- Older news can be found in text format in files NEWS.0, NEWS.1, NEWS.2 and and NEWS.3 in the ‘doc’ directory. News in HTML format for R versions 3.x and from 2.10.0 to 2.15.3 is available at NEWS.3.html and NEWS.2.html.