Reference

1 Unit systems

units.read_xml([path])

Reads a units database in XML format and returns a unit system. If the path to the database is ommitted, the function reads the path specified in the environment variable UDUNITS2_XML_PATH; or, if unset, the default database.

system:get_dimensionless_unit_one()

Returns the unit of dimension 1.

system:get_unit_by_name(s)

Returns the unit that matches the given name in a case-insensitive manner.

system:get_unit_by_symbol(s)

Returns the unit that matches the given symbol in a case-sensitive manner.

system:parse(s[, encoding])

Parses the given unit string and returns the corresponding unit. A second, optional argument encoding specifies the character encoding of the string.

encoding may be any of the following:

  • “ascii”;
  • “iso_8859_1”;
  • “latin1” (an alias of “iso_8859_1”);
  • “utf8” (the default).

2 Units

x * unit

Returns a unit that equals unit scaled by x.

unit * x

Returns a unit that equals unit scaled by x.

unit1 * unit2

Returns a unit that equals the product of the two units.

x / unit

Returns a unit that equals the inverse of unit scaled by x.

unit / x

Returns a unit that equals unit scaled by the inverse of x.

unit1 / unit2

Returns a unit that equals the quotient of the two units.

unit ^ n

Returns a unit that equals unit raised to the power of n.

unit % x

Returns a unit that equals unit offset by x.

unit1 == unit2

Returns true if the two units belong to the same unit system and are equal; otherwise returns false.

tostring(unit)

Returns a string representation of unit in ASCII character encoding.