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.