Units

 add or modify a system of units

Parameters

 system - symbol; system name opts - (optional) equation of the form $'\mathrm{check}'=$ true or false; specify options for the system units - symbol; any number of existing units to be associated with the given system.

Description

 • The AddSystem(unit_name, opts, units) function adds or redefines a system of units in the current session.
 • This allows you to specify it for a call to the UseSystem command.
 • A system cannot have two units with the same dimension.
 • The opts argument can contain the following equation.
 $'\mathrm{check}'=$ truefalse
 If this option is set to true, an exception will be generated if two units with the same dimension are associated with the system. Otherwise, the last unit with the given dimension will be associated with the system. The default value of 'check' is false.
 • Units to be associated with the given system are listed.

Examples

 > $\mathrm{with}\left(\mathrm{Units}\right):$
 > $\mathrm{AddSystem}\left('\mathrm{US_Survey}','\mathrm{check}','\mathrm{mile}\left[\mathrm{US_survey}\right]'\right)$
 > $\mathrm{UseSystem}\left('\mathrm{US_Survey}'\right)$
 > $\mathrm{with}\left(\mathrm{Units}\left[\mathrm{Standard}\right]\right):$

Notes:

 – To enter a unit in 2-D Math input, select the unit from the appropriate Units palette. If the unit you want is not there, select $\mathrm{unit}$ and then enter the unit.
 – When you edit a unit, double brackets appear around it.
 > $3\mathrm{Unit}\left('m''\mathrm{ft}'\right)$
 ${3}{}⟦{m}{}{\mathrm{ft}}⟧$ (1)
 > $\mathrm{combine}\left(,'\mathrm{units}'\right)$
 $\frac{{1968496063}}{{5575680000000000}}{}⟦{{\mathrm{mi}}}_{{\mathrm{US_survey}}}^{{2}}⟧$ (2)
 > $\frac{\mathrm{Unit}\left(m\right)}{\mathrm{Unit}\left(m\right)}$
 $\frac{{1968496063}}{{5575680000000000}}{}⟦{{\mathrm{mi}}}_{{\mathrm{US_survey}}}^{{2}}⟧$ (3)
 > $\mathrm{AddSystem}\left('\mathrm{FHF}','\mathrm{check}','\mathrm{furlong}','\mathrm{hundredweight}\left[\mathrm{long}\right]','\mathrm{fortnight}','\mathrm{second}'\right)$
 > $\mathrm{AddSystem}\left('\mathrm{FHF}','\mathrm{check}','\mathrm{furlong}','\mathrm{hundredweight}\left[\mathrm{long}\right]','\mathrm{fortnight}'\right)$
 > $\mathrm{UseSystem}\left('\mathrm{FHF}'\right)$
 > $a≔\mathrm{Unit}\left(\frac{'\mathrm{cm}'}{'\mathrm{min}'}\right)$
 ${a}{≔}⟦\frac{{\mathrm{cm}}}{{\mathrm{min}}}⟧$ (4)
 > $\mathrm{convert}\left(a,'\mathrm{system}'\right)$
 $\frac{{1400}}{{1397}}{}⟦\frac{{\mathrm{furlong}}}{{\mathrm{fortnight}}}⟧$ (5)
 > $43\mathrm{Unit}\left('\mathrm{newton}'\right)+15\mathrm{Unit}\left('\mathrm{poundal}'\right)$
 $\frac{{58415676313069440000}}{{9052407727}}{}⟦\frac{{\mathrm{furlong}}{}{{\mathrm{hundredweight}}}_{{\mathrm{long}}}}{{{\mathrm{fortnight}}}^{{2}}}⟧$ (6)