Defining new unit (year, century) in siunitx

Question

I'm having a hard time figuring out the LaTeX commands to define new units of year and century in siunitx.

I'd like to write \SI{3}{\cm\per\year} and have it show: 3 cm yr-1, or \SI{42}{\micro\meter\per\century} become 4.2E-5 m/century

You can just write \SI{3}{\cm\per yr}, pehaps you could add a little more detail to your question?
I should point out that you won't get the second of your two examples to work. siunitx can convert prefixes into powers, but does not then attempt to update the number to account for this. I guess I can add this as a feature request for v2.2.

Joseph Wright · Accepted Answer · 2010-11-26 22:08:10Z

up vote 8 down vote accepted

In your preamble

\DeclareSIUnit\century{century}
\DeclareSIUnit\year{yr}

See the siunitx manual (v2.1 series), Section 4.5, page 12.

answered Nov 26 '10 at 22:08

Joseph Wright♦
80.7k5203359

	I have added `\DeclareSIUnit\annum{a}`, but it does not seem to have any effect. How to I find out what version I'm using? – mankoff Dec 1 '10 at 17:49
	Add `\listfiles` to your source and look in the log. I'd be interested to see an example of this: perhaps you can post one here. – Joseph Wright♦ Dec 1 '10 at 18:01
	OK, I'm using v1.0i (2008/08/14), probably because my LaTeX is via OS X `fink install texlive` which is v 2008. I presume an example is no longer necessary. – mankoff Dec 1 '10 at 18:24
	Okay, in that case you want `\newunit\annum{a}`. (I'd also note that it is generally recommended to use MacTeX or vanilla TeX Live on OS X, rather than using one of the ports, as you get a much more up to date system.) – Joseph Wright♦ Dec 1 '10 at 19:12

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