Re: [yt-users] Athena units

Ah, sorry for the misinformation! On Tue, Oct 22, 2013 at 9:36 AM, John ZuHone wrote:

But, "z-velocity" is a defined derived field in the Athena frontend, and should give it in CGS units.

On Oct 22, 2013, at 12:32 PM, Nathan Goldbaum wrote:

Yes, velocity_z is in code units as well because it's an athena field. You'll need to define a new x-velocity field (to match the naming scheme elsewhere in yt) that converts the athena velocity field to CGS.

This is all being fixed with our new sympy powered units system and will be much easier in yt 3.0 or 3.1 (whichever version gets the new units support).

-Nathan

On Tue, Oct 22, 2013 at 9:23 AM, John ZuHone wrote:

...

Hi Stephanie,

First off, if I recall correctly we only support setting LengthUnits, DensityUnits, and TimeUnits. Everything else (such as mass, velocity, energy, etc.) should be derived from those.

Secondly, the reason why you're seeing this for the grid "z" is that it always defaults to the code units (as well as "x" and "y", and the cell deltas). I don't think we have a built-in field for "z" in centimeters (or anything else other than code units), so I think you might have to define a field on your own for "z" in whatever units you want.

Anyone else want to chime in?

Best,

John

On Oct 22, 2013, at 11:31 AM, Stephanie Tonnesen wrote:

Hi John,

Thanks for this. So I now have this in, and it is being applied to my SlicePlot and ProjectionPlot, but my pc.add_phase_object is still using code units. There is an excerpt below.

...

pf = load("id0/rps."+outstring[i]+".vtk",parameters={"TimeUnits":9.78262,"LengthUnits":26.,"DensityUnits":9.999e-30,"VelocityUnits":2.6e3,"MassUnits":2.596e6}) pc = PlotCollection(pf) tracerp25 = alld.cut_region(["grid['specific_scalar[0]'] > 0.25", "grid['z'] > 0.01"])

...

pc.add_phase_object(tracerp25,["z","velocity_z","CellMass"],weight=None,x_log=False,y_log=False)

Can I force it to use physical units?

Thanks, Stephanei

On Mon, Oct 21, 2013 at 10:24 PM, John ZuHone wrote:

...

Stephanie,

You can set it up like this:

pf = load("virgo_weak_mag.0054.vtk", parameters={"TimeUnits":3.1557e13, "LengthUnits":3.0856e24,

"DensityUnits":6.770424595218825e-27})

Sorry, this is a little-documented feature.

Best,

John

On Oct 21, 2013, at 10:20 PM, Stephanie Tonnesen wrote:

...

Hi Again, Everyone!

So I would also like my figures to be in physical units, instead of in my code units. I *think* the Athena frontend doesn't read in what the unit conversions are (and I am not sure how it would do that). Can I just do something simple like:

DensityUnits = 3. density_physunits = grid['density'] * DensityUnits

Then, of course, I don't know how I would do a SlicePlot, ProjectionPlot or phaseplot in physical units...

Any help/advice/direction is appreciated!

Thanks, Stephanie _______________________________________________ yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

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