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Topic: Quantity
Replies: 1   Last Post: Sep 26, 2013 3:45 AM

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Sseziwa Mukasa

Posts: 108
Registered: 8/26/07
Re: Quantity
Posted: Sep 26, 2013 3:45 AM
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The question now being asked:

> Is there a method to create a list of unit strings
> known to the kernel, i.e., those that would not involve a query
> to Wolfram Alpha?

is a little different than the original question, which was what are the possible units. I don't think it's too difficult although perhaps tedious to answer the new question: download the list from NIST, turn off the computer's internet connection, restart Mathematica (to clear any cached values, otherwise I'm not so sure how to do that) and then test whether Mathematica understands all the units from the NIST list.

On Sep 25, 2013, at 2:35 AM, Bill Rowe <readnews@sbcglobal.net> wrote:

> On 9/24/13 at 4:16 AM, itais@wolfram.com (Itai Seggev) wrote:

>> On Sun, Sep 22, 2013 at 02:47:41AM -0400, Bill Rowe wrote:
>>> There does not seem to be a specific set of unit strings. Note that
>>> doing:

>>> In[1]:= UnitConvert[Quantity[12., "Feet"], "Meters"]
>>> Out[1]= 3.6576 m
>>> returns a result essentially immediately. But doing
>>> In[2]:= UnitConvert[Quantity[12., "Foot"], "Meters"]
>>> Out[2]= 3.6576 m
>>> returns the same result after a small delay. You should see a brief
>>> message indicating Mathematica is interpreting the units. I believe
>>> what is happening here is Mathematica is using Wolfram Alpha to
>>> interpret the unit string which increases the allowable number of
>>> unit strings significantly and makes it essentially impossible for
>>> a user to create a list of allowable unit strings.

>> I'm not sure if you are complaining about or praising the
>> flexibility of input,

> Neither. I was simply trying to show why it would be difficult
> to enumerate a specific list of units Mathematica can utilize.

>> but you can always see the canonical unit name
>> by looking at the InputForm.

>> In[3]:= Quantity[5, "Foot"]//InputForm
>> Out[3]//InputForm=Quantity[5, "Feet"]

> True. But this doesn't really answer the original poster's
> question. Is there a method to create a list of unit strings
> known to the kernel, i.e., those that would not involve a query
> to Wolfram Alpha?

>> You can also turn off internet connectivity in the preferences if
>> you don't want Quantity to try to interpret units for you by asking
>> W|A.

> I am happy with Mathematica asking Wolfram Alpha. That generally
> makes my life simpler. But I can also see why it might be nice
> to have a list of unit strings Mathematica will work with
> without asking Wolfram Alpha.

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