On Aug 13, 2:11 pm, "Dr. David Kirkby" <david.kir...@onetel.net>
wrote:
> Jonathan wrote:
>
> > On Aug 13, 12:01 pm, "Dr. David Kirkby" <david.kir...@onetel.net>
> > wrote:
> >> Jonathan wrote:
> >>> As a physical scientists I am definitely excited about this. I think
> >>> the basic plans are sound.
> >>> I presently do units as symbolic variable defined in terms of a list
> >>> of standard SI units. I also define a list of physical constants with
> >>> units. This works quite well, but as mentioned by others this means
> >>> everything ends up expressed in terms of the fundamental units. I
> >>> then either have to recognize what derived unit the fundamental
> >>> expression is or divide it by derived units to see what I have.
> >>> So here are the key things beyond the already existing functionality
> >>> that would be ideal:
> >>> 1) Automatic look up of physical units and their uncertainties at the
> >>> NIST web site. I think the package should maintain a table and then
> >>> have a check_physical_constants() function.
> >> That might be a bit difficult. They are not in any easily accessible
> >> format.
>
> >> It is interesting that the charge on an electron returned by Mathematica
> >> (or Wolfram Alpha) is not the recommended value. Both NPL in the UK and
> >> NIST reference some document (2006 I think), yet WRI's value is not that
> >> value. It is however correct within the uncertainty of the measurement.
> > NIST supplies a simple table format. I even started to write a
> > parser, but I'm a lot better at parsing in perl and java, so decided I
> > didn't have time. If somebody wants to tackle the parsing, I can
> > probably dig up the link.
>
> > Jonathan
>
> I would worry a bit about automatic updating of values, in case things
> go wrong on the NIST web site.
>
> I think it would be better to update them on a new release of sage. The
> constants don't change that often - a bit of a play on words there.
>
> Dave
I think you are partially correct. There should be a set of physical
constants included in SAGE which should be checked by hand and updated
at some regular interval.
I still think it worth trying to include an update function that the
user can call. This function could try to go to one or more web sites
and download the data. If the data is not there in the expected form
it should generate an error message. If might also be wise to
generate a list of changes and ask the user to accept them. Then if
things are weird the user is likely to catch it. I think this is
doable, but at this point is I don't have time or the necessary
parsing experience in python to do this.
Jonathan
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send an email to sage-devel@googlegroups.com
To unsubscribe from this group, send an email to
sage-devel-unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sage-devel
URLs: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
