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Unit interpretation gives an error (version 11.3)

Dan Stimits
Posted 1 year ago

Hi,

I am using Mathematica 11.3 on Linux, and I've found what appears to be a bug regarding units. I'm trying to enter some aircraft maximum roll rates in units of degrees per second. An example which results in an error: x = Quantity[150.0, "Degrees"/"Seconds"]

This seems to be related to a bug in handling this version having Wolfram Alpha access end in October 2023 (it isn't that date yet, but even if it were, when I specify units I can't get some units to work).

The result of entering that is "Quantity: Unable to interpret unit specification Degrees/Seconds."

Even so, I can easily use something like this: y = Quantity[150.0,"Meters"/"Seconds"]

I tried separating this into: x = Quantity[150.0, "Degrees"] / Quantity[1.0/"Seconds"]

The above also fails with the same error. If I multiply the variable by 2, nothing happens, and so I have to conclude this is not a warning, but an actual error. Is Wolfram Alpha required to use units? If so, and if Alpha access continues until October, why is it not possible to specify Degrees/Seconds, whereas I can specify Meters/Seconds? Is there a workaround? Is Quantity a purely Wolfram Alpha thing?
POSTED BY: Dan Stimits
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BTW there is a missing comma in the assignment of θ_roll and in V13.2 all input lines work
POSTED BY: Ahmed Elbanna
Dan Stimits
Dan Stimits
Posted 1 year ago

Thank you, That was my real problem. I do have to give credit to @Gianluca Gorni as well, since it turns out I also am running into issues of AngularDegrees at times. I think I learned to (A) look closer at commas, and (B) use //InputForm more for documentation questions when I don't see something.
POSTED BY: Dan Stimits

With the release of version 13.2 there was a discussion about the new temperature difference concept. This made me curious about the possible ambiguities between angular and temperature degrees. I happened to try something like this:

In[117]:= Quantity[10, "Degrees"] // InputForm

Out[117]//InputForm=
Quantity[10, "AngularDegrees"]

and that's how I met "AngularDegrees".
POSTED BY: Gianluca Gorni
Dan Stimits
Dan Stimits
Posted 1 year ago

I don't know if Wolfram reads these, but I have version 11.3, and it also shows AngularDegrees after InputForm, but there is no mention at all in documentation (though it might be a non-issue since you have this in documentation of your release). So I'm guessing it is a bug of release 11.3 documentation. On the other hand, I don't know why, if it automatically converts to a default of AngularDegrees, that specifically using that somehow solves my particular issue.
POSTED BY: Dan Stimits

You may try the full name "AngularDegrees" instead of the abbreviation "Degrees", which requires an intepretation, because it could possibly refer to temperature degrees.
POSTED BY: Gianluca Gorni
Dan Stimits
Dan Stimits
Posted 1 year ago

Thank you, that works!

This did, oddly enough, lead me to find an unexpected bug: There is no documentation on AngularDegrees. Nothing is found if I read documentation and all references when looking up

  • Degrees
  • Angular
  • AngularDegrees
  • Quantity

My question now is: If the regular documentation does not have, then where did you find it? I'm using version 11.3, so maybe it's too old, but the quantity does work with that (which says this version was intended to have that).
POSTED BY: Dan Stimits
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