About:
GNU `units' converts between different systems of units. It can handle multiplicative scale changes as well as nonlinear conversions, such as Fahrenheit to Celsius. Over 2000 units definitions are included in a well-annotated data file.

Release focus: Minor feature enhancements

Changes:
Units now reads custom definitions from ~/.units.dat. The precedence of "*" has changed to match the usual algebraic precedence, and the "**" operator was added for exponents. A text search feature was added so that typing "search text" lists the units whose names contain "text".

Author:
Adrian Mariano [contact developer]

Rating:	reset 1 2 3 4 5 6 7 8 9 10
8.38/10.00 (1 vote)

Homepage:
http://www.gnu.org/software/units/units.html
Tar/GZ:
ftp://ftp.gnu.org/pub/gnu/units/units-1.87.tar.gz

Trove categories: [change]

[Environment]		Console (Text Based)
[Intended Audience]		End Users/Desktop
[License]		OSI Approved :: GNU General Public License (GPL)
[Operating System]		Microsoft :: Windows, POSIX
[Programming Language]		C
[Topic]		Scientific/Engineering, Utilities

Dependencies: [change]
No dependencies filed

 Branches

Branch	Version	Last release	License	URLs
Default	1.55	01-Aug-1999	GNU General Public License (GPL)
Development	1.87	27-Sep-2007	GNU General Public License (GPL)

 Releases

Version	Focus	Date
1.87	Minor feature enhancements	27-Sep-2007 09:18
1.86	Major bugfixes	16-Nov-2006 12:25
1.85	Minor feature enhancements	31-May-2005 05:31
1.80	Minor feature enhancements	20-Jun-2002 05:21

 Comments

[»] non-linear?
by T. Lüttgert - Jun 20th 2002 04:21:54

Maybe this is nit-picking, but Fahrenheit <-> Celsius is a perfectly linear conversion:

T[C] = (T[F]-32)/1.8

non-linear would be Energy to Wavelength, for example.

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[»] Re: non-linear?
by Adrian Mariano - Jun 20th 2002 07:52:08


> Fahrenheit <-> Celsius is a
> perfectly linear conversion:
>
> T[C] = (T[F]-32)/1.8
No, it is an affine transformation, not a linear one because of the constant offset. If F is a linear transformation then it must satisfy the property F(a+b)=F(a)+F(b). This is clearly false for the above temperature conversion. For example 32 degrees Fahrenheit is 0 degrees Celsius but 32+32=64 degrees Fahrenheit is not 0+0=0 degrees Celsius.

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[»] Re: non-linear?
by Eivind Magnus Hvidevold - Jun 14th 2005 04:30:09

A linear function is of the form f(x) = ax + b, while a linear transformation satisfies T(a + b) = T(a) + T(b). So the "function" is linear, but the "transformation" is not. Of course, the function and the transformation is the same, so it depends on the context which one applies. A transformation is obviously what the units developers had in mind, and that is probably natural given that units are transformed to other units.

--
EMH

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