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This package provides backports of functions which have been introduced in one of the base packages in R version 3.0.1 or later.The backports are conditionally exported in order to let R resolve the function name to either the implemented backport, or the respective base version, if available.Package developers can make use of new functions or arguments by selectively importing specific backports to support older installations.

Attach the namespace vialibrary(backports).

Note that it is crucial thatbackports is build against the currently running R version.Do not ignore these kind of warnings for this package.

1. Add backports to your DESCRIPTION underImports.
2. Add or modify the function.onLoad() (seehere) to call theimport() function of backports:

   .onLoad<-function(libname,pkgname) {backports::import(pkgname)}

   You can also selectively import functions:

   .onLoad<-function(libname,pkgname) {backports::import(pkgname, c("get0","dir.exists"))}

   If you setforce = TRUE, the provided functions will get imported, regardless of the R version:

   .onLoad<-function(libname,pkgname) {backports::import(pkgname,"hasName",force=TRUE)}

3. [Optional] SetDepends in your DESCRIPTION to requireR (>= 3.0.0).

Backports for functions which are not in thebase require additional steps.Usually, you need to to import those functions in the package NAMESPACE.However, this is only possible if such a function really exists, and yields a warning duringR CMD check for older versions.There are three possibilities to deal with this:

1. Completely import the namespaces instead of selectively importing them, e.g. useimport(utils) instead ofimportFrom(utils, hasName) in yourNAMESPACE file.
2. Force-import the function (see above) so that you always use the backport instead of the implementation shipped with R, even for the most recent version of R.
3. Use a conditional import in yourNAMESPACE file, e.g.

   if (getRversion() >= "3.4.0") {  importFrom(utils, hasName)} else {  importFrom(backports, hasName)}

Note that the braces{} are necessary in theNAMESPACE file, even though they wouldn't be for regular R code, and that you might get a warningfor includingbackports in theImports: section of yourDESCRIPTION file if you never end up using it.

• base::anyNA()
• base::dir.exists()
• base::file.size(),base::file.mode() andbase::file.mtime()
• base::lengths()
• Argumentextra_cols forbase::file.info()
• Argumentrepeated forutils::URLencode
• base::isNamespaceLoaded()

• base::startsWith() andbase::endsWith()
• base::strrep()
• base::trimws()
• Argumenttype forutils::capture.output()

• base::.valid.factor()
• utils::hasName()

• base::...length()
• base::...elt()
• base::isFALSE()

• base::warningCondition()
• base::errorCondition()
• Argumentq forbase::dQuote() andbase::sQuote()
• tools::vignetteInfo()
• base::str2lang()
• base::str2expression()
• base::asplit()
• utils::removeSource() with the capability to strip source from language objects.

• base::deparse1()
• base::list2DF()
• tools::R_user_dir()
• Argumentclasses forbase::suppressWarnings() andbase::suppressMessages()

• Argumentrecycle0 forbase::paste().
• Argumentrecycle0 forbase::paste0().

• base::...names()
• base::.libPaths()

• tools:::print.Rconcordance
• tools:::as.character.Rconcordance
• tools::as.Rconcordance
• tools:::as.Rconcordance.default
• tools::matchConcordance