python-quantities-developers team mailing list archive

[Tony S Yu <tonyyu@xxxxxxx>]

Hi Darren,

On Jul 11, 2009, at 6:44 PM, Darren Dale wrote:
> Please take a moment to consider the following, which is included in  
> the tutorial at http://packages.python.org/quantities/user/tutorial.html 
>  :
>
> ---
> One final note: Quantities is not a package for describing  
> coordinate systems that require a point of reference, like positions  
> on a map or absolute temperature scales. Proper support of  
> coordinate systems would be a fairly large undertaking and is  
> outside the scope of this project.
> ---
>
> I would argue that the current behavior is correct, because  
> quantities assumes that degC (for example) is a temperature  
> difference, not an absolute temperature. So I would opt not to apply  
> this patch.

Hmm, I think I read this note when I first started using quantities,  
but I completely forgot about it. I agree that this feature would be  
pretty difficult to add and understand why it'd be out of the scope of  
this project. (Now that I think about it, I can't imagine how one  
would distinguish between temp differences and absolute temps).

However, I think this would be a common "gotcha" for users who want to  
convert temperatures, and deserves a slightly more prominent mention  
than the note above. FWIW, I would suggest putting the "One final  
note" under a restructuredtext admonition (maybe, "important" or  
"attention" with appropriate styling to give it emphasis).

> I would rather not include the discussion about interpolation, since  
> this does not seem specific to quantities.

I agree it's not really a quantities issue. I actually added it to  
issues.rst before realizing that it wasn't an error caused by  
quantities and probably should have removed it subsequently.

Thanks for your feedback.
-Tony