units 0.7-0

• add load_units_xml to enable database reloading as well as loading
  user-provided unit systems; #254 addressing #243, #244

• add install_unit and remove_unit for adding/removing custom user-defined
  symbols or names, with optional mapping to existing units;
  install_symbolic_unit, remove_symbolic_unit, install_conversion_constant,
  install_conversion_offset are deprecated; #261 addressing #89

• add keep_units, a helper to apply functions that do not preserve units;
  #255 addressing #252

• fix as_units(""), which is now equivalent to unitless; #199

• fix plot axes for plot.formula and plot.data.frame; #213

• fix arithmetic for powers above 1 and below -1; #264

• improve arithmetic of logarithms; #249

• export ud_are_convertible; #263 addressing #258 @cregouby

• remove deprecations: as.units, as_cf, make_unit, parse_unit; #259

• remove deprecated pre-computed ud_units database; #259

units 0.6-7

• port isFALSE to fix regression in old R versions; #230 addressing #229

• fix replacement operation for units objects; #233 addressing #232

• fix compatibility with dplyr 1.0; #247 addressing #239

units 0.6-6

• prettier str print for units and mixed units; #228 addressing #227

• add compatibility with upcoming tibble v3.0.0; #225

units 0.6-5

• skip test on CRAN to avoid issues with strict latin1 environments

units 0.6-4

• fix support for weights with units in weighted.mean; #205

• invalid names for new units now trigger a proper error message; #209 addressing #208

• fix issues in strict latin1 environments; #202

units 0.6-3

• improve platform dependent encodings handling; #183

• don't force as.numeric when unnecessary; #182 addressing #181

• fix valgrind issues on CRAN and tidy up tests; #193 addressing #192

• new method drop_units for data frames; #191 addressing #187

units 0.6-2

• fix support for logarithms and decibels; #177 addressing #176

• add delayed S3 registration mechanism for R >= 3.6.0

units 0.6-1

• vectors with mixed units are now supported; #145

• NA values for units now trigger a proper error message; #163

units 0.6-0

• print units as [unit] more consistently, e.g. for single unit and in data.frames; #132

• improve printing of unitless units; provide option to print something else than 1; #150

• fix printing unitless in labels when negative_power is TRUE; #133

• install_symbolic_unit now adds a dimensionless unit, integrated in the units system, meaning that prefixes on it work as well; #71

• install_conversion_constant and install_conversion_offset now install a new unit that is a function of an existing udunits unit.; #71, #84

• unit simplification can now be user-controlled by units_options; #89

• set_units(15, mg/kg) is now no longer simplified to 1e-9 unitless; #89

• directly uses the udunits2 C library; drop dependence on R package udunits2, fixing R package udunits2 memory leaks; #135

• drops %*%, no longer gives warning when loading

units 0.5-1

• deal with trigonometric functions for units degree; return units rad on inverse trigonometric functions.

• Unit creation has been significantly refactored. units<- now accepts strings
  or quoted language objects on the right hand side, powered by new S3 methods for
  as_units. All valid unit symbols and unit names recognized by package 'udunits2' are
  now accepted. New user facing function make_units() (plural s) is also
  provided. See ?as_units for details. @t-kalinowski

• new functions valid_udunits() and valid_udunits_prefixes() generate tidy
  dataframes listing all the valid unit names, symbols, and prefixes recognized by
  udunits. @t-kalinowski

• new function install_symbolic_unit() for adding custom, user-defined units.
  @t-kalinowski

• make_unit and parse_unit (singular unit) have been deprecated, please use
  as_units instead.

• ud_units is no longer necessary and is soft-deprecated, and may be removed
  in a future release.

• add %*% as an S3 generic; #54

• add %% and %/% to Ops.units

• support unary + and - ; #56

• add seq method for units, converting units to those of the first argument

• Deprecate as.dt for as_difftime, as.units for as_units and as_cf for deparse_unit