Defining new units and prefixes

Tip

See also:

• The value expressions section in the marks guide; and

• The units module API documentation.

manim-eng’s unit system defines most of the units you would expect to be using day-to-day, but cannot hope to cover all possible situations (in particular, it doesn’t define any imperial units). Thankfully, the process of defining your own units (and indeed prefixes) is very simple.

Defining units

Units are defined using the Unit class (which is imported by default and doesn’t require a manim_eng.implementation import). The constructor only requires one argument: a string with the unicode representation of the unit.

ERLANG = Unit("E")

manim-eng uses a MathTex to display units. By default, it assumes that the string you passed before when wrapped in \mathrm{} is the correct LaTeX math mode string to represent the unit symbol. If this is not the case, you can use the latex parameter to specify a custom string (it will still be wrapped in \mathrm{}.

MHO = Unit("℧", latex=r"\mho")

Defining prefixes

Within the unit system, prefixes are just considered ‘special’ units that attach themselves to the unit after them and don’t themselves adopt an exponent. To declare a prefix, the process is the same as outlined above for units, except the prefix parameter is set to True:

MYRIA = Unit("my", prefix=True)

As a note, manim-eng defines the following prefixes already:

• The standard SI set of prefixes in jumps of 10³ from 10^-30 (quecto) to 10³⁰ (quetta);

• The other SI prefixes hecto, deca, deci, and centi; and

• The IEC binary prefixes in jumps of 2¹⁰ from kibi (2¹⁰) to yobi (2¹⁰⁰).