[yt-users] Radial velocity Projections

[Matthew Turk]

Hi John,

Yup, you can.  I'm looking at the code right now and I think the issue
is going to be tricky to maneuver through the code base in a reliable
way the field parameters.  Here's what I'd suggest doing --

for grid in pf.h.grids:
    grid.set_field_parameter("center", c)

just before you call OffAxisProjection.  This is something that the
grid machinery is a bit annoying about the way that things work in
2.x, but we're fixing in 3.0.  You'll also have to set the "normal"
field parameter.

Let me know if that works,

-Matt


On Mon, Dec 16, 2013 at 9:55 AM, John Regan <johnanthonyregan at gmail.com> wrote:
> Hi Matt,
>
> Yes it is the OAP I am interested in. I had originally weighted the
> projection using the density field.
>
> The projected velocity may look funny and it would be interesting to try to
> compare that to the planar. Could I also pass cyl_RadialVelocity to the OAP
> API?
>
> Cheers,
> John
>
> On 16 Dec 2013 16:09, "Matthew Turk" <matthewturk at gmail.com> wrote:
>>
>> Hi John,
>>
>> Sorry for the delay in replying.
>>
>> On Fri, Dec 13, 2013 at 8:59 AM, John Regan <johnanthonyregan at gmail.com>
>> wrote:
>> > Hi All,
>> >
>> > I was trying to make an OffAxis radial projection. Naively using
>> >
>> >  proj = OffAxisProjectionPlot(pf, L, "RadialVelocityKMS", center='max',
>> > width=(width, 'pc'),
>> >                                      depth=depth)
>> >
>> > fails with a message of type
>> >
>> > yt.data_objects.field_info_container.NeedsParameter: (['center'])
>> >
>> >
>> > The RadialVelocity probably isn't the field to use here and requires
>> > some
>> > manipulation to be a quantity suitable for plotting.
>> >
>> > Any suggestions on the best way forward would be much appreciated.
>> >
>>
>> So, a few questions.  Do you want to show the way that the radial
>> velocity is distributed, with respect to an image plane that isn't
>> axis aligned?  If you so, you might have more luck using the
>> OffAxisSlicePlot, which will take a slice through the domain.  The OAP
>> plot will integrate along the line of sight; you will probably want to
>> take an average if this is what you want, by supplying the weight
>> parameter here, as otherwise it'll just sum up the RV values at all
>> points.  I think the issue with it not having the parameter center is
>> fixable, but we should probably make sure that's what you're looking
>> for first.  It's also going to be doing the full 3D radial velocity,
>> not the planar velocity, so if your velocity is roughly spherical it
>> might have odd morphology in the resultant plot.
>>
>> If a slice will do what you're looking for, I'd recommend the
>> OffAxisSlicePlot -- if you indeed do want a radial average, then I'll
>> take a look at passing the parameter in.  (This will also help by
>> enabling you to pass in the bulk velocity.)  And if you want to find
>> the planar RV, you'll have to use a field like cyl_RadialVelocity.
>>
>> -Matt
>>
>> > Cheers,
>> > John
>> >
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