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Re: Terrible unit trouble in Mathematic 9

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  • Subject: [mg129209] Re: Terrible unit trouble in Mathematic 9
  • From: jsheinwald <jsheinwald at comcast.net>
  • Date: Fri, 21 Dec 2012 05:39:24 -0500 (EST)
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One problem with the UnitConvert command in Mathematica 9 is that it is not consistent.



In[7]:= a = UnitConvert[Quantity[55, "Miles"/"Hours"], Quantity["Meters"/"Seconds"]]

Out[7]= Quantity[96800/3937, ("Meters")/("Seconds")]

Works.  But so does:


In[8]:= b = UnitConvert[Quantity[78, "Centimeters"/"Seconds"], "Inches"/"Minutes"]

Out[8]= Quantity[234000/127, ("Inches")/("Minutes")]

This, as expected works:


In[9]:= c = UnitConvert[Quantity[0.6, "Radians"], Quantity["Degrees"]]

Out[9]= Quantity[34.3775, "AngularDegrees"]

But this does not:


In[10]:= d = UnitConvert[Quantity[0.81, "Radians"], "Degrees"]

During evaluation of In[10]:= UnitConvert::unkunit: Unable to interpret unit specification Degrees. >>

Out[10]= UnitConvert[Quantity[0.81, "Radians"], "Degrees"]

There are some serious consistency problems with the way unit conversions are implemented in Mathematica 9.  The examples in the help files could use some improvement too.






On Wednesday, December 19, 2012 4:55:49 AM UTC-5, David Reiss wrote:
> You need to get both the syntax right as well as the names of the
> 
> units (which are strings).  E.g.,
> 
> 
> 
> UnitConvert[Quantity[55 , "Miles"/"Hours"],
> 
> Quantity["Meters"/"Seconds"]]
> 
> 
> 
> Go back and spend a bit of time reviewing the documentation and
> 
> working through the examples for the functions that are contained in
> 
> the documentation....  ;-)
> 
> 
> 
> --David
> 
> 
> 
> 
> 
> On Dec 18, 2:35 am, tio54... at gmail.com wrote:
> 
> > I continue to receive "Unable to interpret unit specification m/s" (for example, but almost anything I attempt returns this message) with input:
> 
> > UnitConvert[55 mi/h,"m/s"] or UnitConvert[55 mi/h,m/s] or any other combination of quotes, omitted quotes, etc. Even the prediction/suggestion box,  
> when I execute Quantity[55,"mi/hour"}, after it returns 55 mi/h, if I type in any combination of m/s, "m"/"s", "m/s", etc. into the box that opens when I select "Convert" in the prediction box yields the same "unable to inter=
> 
> pret unit specification.
> 
> >
> 
> > What the heck????




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