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Re: Terrible unit trouble in Mathematic 9

  • To: mathgroup at smc.vnet.net
  • Subject: [mg129220] Re: Terrible unit trouble in Mathematic 9
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Sat, 22 Dec 2012 05:01:19 -0500 (EST)
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The outut from your third example showed you that Mathematica was
expecting you to use "AngularDegrees" as the output units

(d = UnitConvert[Quantity[0.81, "Radians"], "AngularDegrees"]) // InputForm

Quantity[46.40958140559669,
 "AngularDegrees"]

or use WA to discover the appropriate units to use

WolframAlpha["convert 0.81 radians to degrees",
   "ComputableData"][[1]] // InputForm

Quantity[46.4, "AngularDegrees"]


Bob Hanlon


On Fri, Dec 21, 2012 at 5:39 AM, jsheinwald <jsheinwald at comcast.net> wrote:
> 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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