Changes

The units module comes with ConTeXt's default distribution. In MkIV the units module comes built-in, however there is still the option to access the old module and can be accessed its commands via <{{cmd>|usemodule</cmd>}}[units].

However, Additional documentation about units in MkIV is available from the [[http://www.pragma-ade.nl/general/manuals/units-mkiv.pdf Units manual]] ===Using the built-in command=== In MkIV we have integrated an upgrade to this mechanism so if you're using that version you might want can use the built-in {{cmd|unit}} command to skip parse units. Some examples of this are shown below: <texcode>10 \unit{km/h}\unit{10 km/h}\unit{~1 km/h}\unit{KiloMeter/Hour}\unit{10 cubic meter / second}\unit{kilo pascal square meter / second}\unit{kilo pascal square meter / kelvin second }$\unit{10 AC}$\frac{10 \unit{m/s}}{20 \unit{m/s}}${\ss 30 \unit{kilo pascal square meter / second kelvin}}\unit{123.22^-3 km/s}\unit{123.22e-3 km/s}</texcode> ConTeXt will take care of spacing and formatting. The parser is fairly flexible, and the following all work and give the same output. {| ! width="45%"| ! width="10%"| ! width="45%"| |- | <texcode>\unit{10 kg}\unit{10kg}\unit{10 kilo gram}\unit{10 kilogram}\unit{10 Kilo Gram}\unit{10 KiloGram}</texcode>||<context mode=mkiv>\startlines\unit{10 kg}\unit{10kg}\unit{10 kilo gram}\unit{10 kilogram}\unit{10 Kilo Gram}\unit{10 KiloGram}\stoplines</context>|} The command works in text as well as in math mode and spaces are normally ignored. You can define your own command:  <texcode>\defineunits[un][alternative=text,separator=medium]</texcode> Valid separators are <code>cdot</code>, <code>big</code>, <code>medium</code>, and <code>space</code> with the first partbeing the default. You can later tune the rendering with  <texcode>\setupunits[un][separator=cdot]</texcode> In due time there will be a few more options. Numbers are formatted cf the digits mechanism (not discussed here).  ===Using the old units module===

* This runtime loadable module implements a way of defining units. The core macro is <{{cmd>|dimension</cmd>}}, a rather clever one that is able to cooperate with some other dimension related macros. As said, this module enables user to enter:

(Note that the space after <{{cmd>|Second</cmd> }} needs to be explicitly specified; otherwise, it will get eaten.)

* Units act upon signals that they insert in the text, in case no quantity is given you need to start the unit sequence using <{{cmd>|Unit</cmd>}}

This definition means that we can ask for the meaning of a unit using <{{cmd>|unitmeaning</cmd> }} and get a list of used units by saying <{{cmd>|placelistofunits</cmd>}}.

We have to use the command <{{cmd>|unitmeaning</cmd> }} instead of <{{cmd>|meaning</cmd>}}, simply because the latter is a TeX primitive we don't want to lose. We use the label text mechanism for translations.

[[httphttps://www.unceasyunitconverter.educom/~rowlett/units/index.html How Many? A Dictionary of Units of MeasurementEasy Unit Converter]]

* Prefixes: <{{cmd>|Atto</cmd> }} a, <{{cmd>|Femto</cmd> }} f, <{{cmd>|Pico</cmd> }} p, <{{cmd>|Nano</cmd> }} n, <{{cmd>|Micro</cmd> }} μ, <{{cmd>|Milli</cmd> }} m, <{{cmd>|Centi</cmd> }} c, <{{cmd>|Deci</cmd> }} d, <{{cmd>|Hecto</cmd> }} h, <{{cmd>|Kilo</cmd> }} k, <{{cmd>|Mega</cmd> }} M, <{{cmd>|Giga</cmd> }} G, <{{cmd>|Tera</cmd> }} T, <{{cmd>|Peta</cmd> }} P, <{{cmd>|Exa</cmd> }} E (missing: <{{cmd>|Zetta</cmd> }} Z, <{{cmd>|Yotta</cmd> }} Y, <{{cmd>|Zepto</cmd> }} z, <{{cmd>|Yocto</cmd> }} y)* Suffixes: <{{cmd>|Linear</cmd> }} ¹, <{{cmd>|Square</cmd> }} ², <{{cmd>|Cubic</cmd> }} ³, <{{cmd>|Inverse</cmd> }} or <{{cmd>|ILinear</cmd> }} ^-1, <{{cmd>|ISquare</cmd> }} ^-2, <{{cmd>|ICubic</cmd> }} ^-3* Fraction: <{{cmd>|Per</cmd>}}, <{{cmd>|Percent</cmd>}}, <{{cmd>|Permille</cmd>}}, <{{cmd>|Promille</cmd>}}* Time: <{{cmd>|Second</cmd>}}, <{{cmd>|Minute</cmd>}}, <{{cmd>|Hour</cmd>}}, <{{cmd>|Day</cmd>}}, <{{cmd>|Month</cmd>}}, <{{cmd>|Year</cmd>}}* Length, Area, Volume: <{{cmd>|Meter</cmd>}}, <{{cmd>|Angstrom</cmd>}}, <{{cmd>|Foot</cmd>}}, <{{cmd>|Inch</cmd>}}, <{{cmd>|Liter</cmd>}}* Mass, Force and Pressure: <{{cmd>|Gram</cmd>}}, <{{cmd>|Atom</cmd>}}, <{{cmd>|Newton</cmd>}}, <{{cmd>|Pascal</cmd>}}, <{{cmd>|Mol</cmd>}}, <{{cmd>|At</cmd>}}, <{{cmd>|Atm</cmd>}}, <{{cmd>|Bar</cmd>}}, <{{cmd>|Force</cmd>}}* Energy, Electricity and Magnetism: <{{cmd>|Joule</cmd>}}, <{{cmd>|Watt</cmd>}}, <{{cmd>|Cal</cmd>}}, <{{cmd>|Farad</cmd>}}, <{{cmd>|Henry</cmd>}}, <{{cmd>|Ohm</cmd>}}, <{{cmd>|Siemens</cmd>}}, <{{cmd>|Ampere</cmd>}}, <{{cmd>|Coulomb</cmd>}}, <{{cmd>|Volt</cmd>}}, <{{cmd>|Tesla</cmd>}}, <{{cmd>|Gauss</cmd>}}, <{{cmd>|VoltAC</cmd>}}, <{{cmd>|VoltDC</cmd>}}, <{{cmd>|EVolt</cmd>}}, <{{cmd>|Weber</cmd>}}* Temperature: <{{cmd>|Degrees</cmd>}}, <{{cmd>|Kelvin</cmd>}}, <{{cmd>|Celsius</cmd>}}, <{{cmd>|Fahrenheit</cmd>}}* Angle: <{{cmd>|Rad</cmd>}}, <{{cmd>|Deg</cmd>}}, <{{cmd>|Sterant</cmd>}}* Frequency, Optics and Acoustics: <{{cmd>|Hertz</cmd>}}, <{{cmd>|RevPerSec</cmd>}}, <{{cmd>|RevPerMin</cmd>}}, <{{cmd>|Candela</cmd>}}, <{{cmd>|Lux</cmd>}}, <{{cmd>|Bell</cmd>}}* Chemistry and Radiation: <{{cmd>|Atom</cmd>}}, <{{cmd>|Mol</cmd>}}, <{{cmd>|Molair</cmd>}}, <{{cmd>|Equivalent</cmd>}}, <{{cmd>|Bequerel</cmd>}}, <{{cmd>|Sievert</cmd>}}, <{{cmd>|Gray</cmd>}}* Informatics: <{{cmd>|Baud</cmd>}}, <{{cmd>|Bit</cmd>}}, <{{cmd>|Byte</cmd>}}

===Using the built-in command=== In MkIV you can use the built-in <cmd>unit</cmd> command. This time we don't use commands, if only because it is somewhat cumbersome. Let's give Define a few examples:  <texcode>10 \unit{km/h}\unit{10 km/h}\unit{~1 km/h}\unit{KiloMeter/Hour}\unit{10 cubic meter / second}\unit{kilo pascal square meter / second}\new unit{kilo pascal square meter / kelvin second }$\unit{10 AC}$\frac{10 \unit{m/s}}{20 \unit{m/s}}${\ss 30 \unit{kilo pascal square meter / second kelvin}}\unit{123.22^-3 km/s}\unit{123.22e-3 km/s}</texcode> The command works in text as well as in math mode and spaces are normally ignored. You can define your own command:  <texcode>\defineunits[un][alternative=text,separator=medium]</texcode> Valid separators are <code>cdot</code>, <code>big</code>, <code>medium</code>, and <code>space</code> with the first being the default. You can later tune the rendering with  <texcode>\setupunits[un][separator=cdot]</texcode> In due time there will be a few more options. Numbers are formatted cf the digits mechanism (not discussed here).  ===Expressing Physical quantities=== A physical quantity is number plus unit, and should not be split. A simple way to do this follows - define your own macro: <texcode>\define[3]\physicalquantityle{\hbox{#1 \times \lunit{10^#2 #3}}}</texcode> You can then write\physicalquantityle{number}{exponent}{unit} This seems to give better results than any other way I have found of combining digits and units. The full range of variants allow expression of physical quantities with and without exponents, with units in long form or not:<texcode>\define[2]\physicalquantity{\hbox{\unit{#1 #2}}}% \physicalquantity{number}{unit} -- gives short form of unit\define[2]\physicalquantityl{\hbox{\lunit{#1 #2}}}% \physicalquantityl{number}{unit} -- gives long form of unit\define[3]\physicalquantitye{\hbox{#1 \times \lunit{10^#2 #3}}}% \physicalquantitye{number}{exponent}{unit} -- gives short form of unit\define[3]\physicalquantityle{\hbox{#1 \times \lunit{10^#2 #3}}}% \physicalquantityle{number}{exponent}{unit} -- gives long form of unit</texcode>  You can also do ranges of units, that are otherwise messy to code up on an individual basis  <texcode>\define[3]\physicalquantityspread{\hbox{#1\endash \lunit{#2 #3}}}</texcode> You can then write:\physicalquantityspread{start}{end}{unit} 

[[Category:MathSciences]]