Use physical units in AtomGroup objects.

[kain88-de]

There's been a comment on the mailing list that it would be nice to have units attached to the Atomgroup objects.

I think that is a great idea. We can have a look into one of the many packages that provide unit aware numpy arrays.

• astropy.units
• pint

[jbarnoud]

The easiest way would be to copy the unit dict from the reader somewhere accessible from the universe. Yet, this dict could contain unit objects rather than strings.

[orbeckst]

We could then also clean up the hacks in MDAnalysis.units and replace them by more general unit conversions.

[richardjgowers]

We've got a nice system of Attribute or Timestep holding all data now, and
AtomGroups requesting data. It would be cool to make the holders do the
conversion, rather than the requestors. So I'd set the mass Attribute to
have unit=kg and any further use of it would give those units.

On Wed, 16 Dec 2015 02:17 Oliver Beckstein notifications@github.com wrote:

We could then also clean up the hacks in MDAnalysis.units and replace
them by more general unit conversions.

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[richardjgowers]

https://unyt.readthedocs.io/en/latest/usage.html

[tylerjereddy]

Also worth noting that facilitating third-party dtype specification is on the NumPy roadmap so if there is specific feedback re: things that MDA needs to make this easier I can relay that information. Be able to write the dtype in pure Python is on the roadmap, albeit somewhat ambitious for more useful dtypes.