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MathGroup Archive 2002

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RE: Units

  • To: mathgroup at
  • Subject: [mg32424] RE: [mg32414] Units
  • From: "David Park" <djmp at>
  • Date: Sat, 19 Jan 2002 19:03:21 -0500 (EST)
  • Sender: owner-wri-mathgroup at


I am not quite certain what you mean by "automatically converted". In any
case, I have a pair of packages at my web site called V4ExtendUnits and
V4ReducedUnits which significantly extends and simplifies the standard Units
package. There is also a tutorial.

ReducedUnits allows you to define unit systems in which some of the physical
constants are set equal to 1. This allows you to implement, for example,
atomic units, which may be what you are looking for, or geometrical units.
ExtendUnits has a routine that allows you to deunitize an expression so that
the input and output variables have specified implied units. This is useful
in doing numerical and graphical work. There are even routines that allow
you to install your own units and use them just like the Mathematica
supplied units. So, you could, for example, use KeV instead of Kilo

One rule that I find useful when working with units is: Don't put explicit
units in the equations. Put the units in the data. Solve the equations and
then substitute the data with the explicit units.

David Park
djmp at

> From: Juan Fuentes [mailto:jfuentes at]
To: mathgroup at
> Dear colleagues:
>  Could any one say me about a package to work in solving
> physics problems in the area of semiconductor physics where the units are
> authomatically converted? Thanking in adavance, Juan

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