[SciPy-Dev] Updating constants

Vincent Davis vincent@vincentdavis....
Fri Jun 11 21:31:00 CDT 2010


On Fri, Jun 11, 2010 at 1:05 PM, Vincent Davis <vincent@vincentdavis.net> wrote:
> On Fri, Jun 11, 2010 at 12:55 PM, Charles R Harris
> <charlesr.harris@gmail.com> wrote:
>>
>>
>> On Fri, Jun 11, 2010 at 12:46 PM, Vincent Davis <vincent@vincentdavis.net>
>> wrote:
>>>
>>> On Thu, Jun 10, 2010 at 11:29 PM,  <josef.pktd@gmail.com> wrote:
>>> > On Fri, Jun 11, 2010 at 1:09 AM, Vincent Davis
>>> > <vincent@vincentdavis.net> wrote:
>>> >> On Thu, Jun 10, 2010 at 10:54 PM, Vincent Davis
>>> >> <vincent@vincentdavis.net> wrote:
>>> >>> On Thu, Jun 10, 2010 at 10:38 PM,  <josef.pktd@gmail.com> wrote:
>>> >>>> On Fri, Jun 11, 2010 at 12:11 AM, Vincent Davis
>>> >>>> <vincent@vincentdavis.net> wrote:
>>> >>>>> The current constants in scipy are from 2002, the newest set
>>> >>>>> available
>>> >>>>> are from 2006.
>>> >>>>> Should they be updated, What are the issues with updating with
>>> >>>>> regard
>>> >>>>> to notifying users ie documenting the update.
>>> >>>>
>>> >>>> I thought these are constants. Did they change the value of Pi
>>> >>>> recently?
>>> >>>
>>> >>> They found more digits of Pi :)
>>> >>> I was referring to "Fundamental Physical Constants"
>>> >>> scipy.constants.codata
>>> >>> I don't know, it's not easy to compare. I assume there was a reason
>>> >>> they updated the list. There is an Uncertainty value on many of them
>>> >>> so I assume the actual value don't change but our estimate does.
>>> >>>
>>> >>> http://physics.nist.gov/cuu/Constants/index.html
>>> >>> release dates 1986, 1998, 2002, 2006
>>> >>>
>>> >>> Vincent
>>> >>>
>>> >>>>
>>> >>>> just curious: What has changed?
>>> >>>>
>>> >>
>>> >> I just relived I can update the constants and then compare them with
>>> >> the old. Should be quick, I will send out the diff in the morning.
>>> >
>>> > quote from the REVIEWS OF MODERN PHYSICS paper:
>>> >
>>> > "Although just four years separate the 31 December closing dates of
>>> > the 2002 and 2006 adjustments, there are a number of important new
>>> > results to consider. Experimental advances include the 2003 Atomic
>>> > Mass Evaluation from the Atomic Mass Data Center (AMDC),which provides
>>> > new values for the relative atomic masses Ar(X) of a number of
>>> > relevant atoms; a new value of ..."
>>>
>>> Ok a few more issues/question about constants.codata.
>>> Some of the names seem rather messed up because of how the raw text is
>>>  read. For example
>>> Loschmidt constant (273.15 K, 101.325 kPa)             2.686 7774 e25
>>>      0.000 0047 e25        m^-3
>>>
>>> The above line gets added to the physical_constants dict with the key
>>> value 'Loschmidt constant (273.15 K, 101.325 kPa)'.
>>> codata.value('Loschmidt constant (273.15 K, 101.325 kPa)')
>>> 2.6867773000000001e+25
>>>
>>> Seems like it should be no more that 'Loschmidt constant' and I would
>>> recommend 'Loschmidt' unless there is a conflict.
>>>
>>
>> The new codata will need a bit of editing to work, for examples the columns
>> used to extract the various parts will need modification. I think "Loschmidt
>> constant" is the right name to use, but this "constant" depends on
>> temperature and pressure, so that should be noted somewhere, maybe in the
>> documentation.
>
> Thats what I was thinking. I could add an additional item to the list
> stored values, "notes", [value, precision, units, notes] and add a
> helper function like the others have ie codata.notes(Loschmidt) =
> (273.15 K, 101.325 kPa)
>
> Does that sound ok?

I have attached a file that when run makes it easy to see what has
changed in the constants (modified from the codata file). If
interested review and give me any feedback you have about the changes.
and how best to document the update.

Vincent

>
> Vincent
>
>
>>
>> Chuck
>>
>>
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>> http://mail.scipy.org/mailman/listinfo/scipy-dev
>>
>>
>
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