
Re: Terrible unit trouble in Mathematic 9
Posted:
Dec 22, 2012 5:01 AM


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@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 UTC5, 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...@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???? > >

