Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

issues with unit package

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88634] issues with unit package
  • From: Jay Ortiz <omaha8master at yahoo.com>
  • Date: Sat, 10 May 2008 06:54:10 -0400 (EDT)

Why won't Mathematica when using the Units package eliminate reciprocal units?   Consider an example from E&M, finding the wavelength corresponding to a frequency:

<<Units`
<<PhysicalConstants`

In[1]:=
 Freq=100*^6 Hertz;
  Wavelength=SpeedOfLight/Freq
Out[1]=(149896229*Meter)/(50000000*Hertz*Second)
In[2]:=N[Wavelength]
Out[2]=(0.299792*Meter)/(Hertz*Second)

i.e. Mathematica doesn't know that Meter/(Hertz Second) should reduce to Meter.   Shouldn't this be handled?

Another example; shouldn't Mathematica reduce expressions in consistent units to a single result?    Example:

In[5]:=3 Ohm + 1 Volt/Ampere
Out[5] =  3 Ohm + 1 Volt/Ampere

Why not 4 Ohm, or 4 Volt/Ampere?   After all, the documentation entry for Ohm says it's equivalent to Volt / Ampere, so it's reasonable that Mathematica would be aware of that relationship.  Doing SI[] or MKS[] on those expressions doesn't change anything.

Maybe the Units package doesn't extend to manipulating variables with quantities that have units.  Am I missing something here?

Thanks.


  • Prev by Date: Re: tablename[[x]]= xth row, how to get xth column
  • Next by Date: Re: A Mathematica implementation of SolvOpt
  • Previous by thread: Re: Bug in Plot?
  • Next by thread: Re: issues with unit package