[yt-users] Calculation of enclosed mass for a given radius

[Latif]

Hi Matt,
Many thanks!

> 1) You have to do the derived field before your pf is loaded; this
> will hopefully change at some point.  You're also using add_field here
> as would normally be done for a profile, but you're using it to define
> a new derived field.


Sorry, i did not explain it very well. Yes, you are very right one has to
add a new derived  field before loading a pf. I used add_field here as i
wanted to make use of it for computing profiles at the moment.

> 2) We have "CellMassMsun" and "CellMass" fields already -- which do
> what you're looking to do.  You should be able to do exactly what you
> are doing,
>
As you know "CellMass" is not computing the enclosed mass( it does not sum
up the mass with in a certian radius) . Prof.add_fields with accumulation
flag true computes the enclosed mass radial profile. What i want is to
store the computed enclosed mass in a new profile field or variable  so
that i can make use of it to compute other profiles like keplerian velocity
etc. At the moment i do not know how to store enlcosed mass. That is why  i
thought to add a new prof field for this purpose. Does it make sense?
Please let me know it is not clear.
Cheers
Latif

>
> prof.add_fields(["CellMass"], accumulation=True, weight=None)
>

which will sum from the low bins to the high bins.  I don't think you
> need any additional derived fields.
>
> Does that help?  We'll add a recipe to do this to the cookbook.
>
> -Matt
>
> On Thu, Jul 19, 2012 at 7:41 AM, Latif <latifne at gmail.com> wrote:
> > Hi Guys,
> > I want to compute the enclosed mass for a given radius to make use of it
> for
> > computing other quantities. I would like  to define a new field like
> > EnclosedMass. How can i use accumulation flag in combination with new
> > defined field to compute the enclosed mass(like in prof.add_fields case).
> > Unfortunately, add_field does not accept it. May be there be there is
> > another way to do this.  Any help in this regard will appreciated.
> >
> > prof.add_fields("CellMass",weight=None,accumulation=True)
> >
> > def EnclosedMass(field,data):
> >     return data["Density"]*data["CellVolume"]
> >
> > add_field("EnclosedMass",
> > function=EnclosedMass,weight=None,accumulation=True)
> >
> > Thanks in advance!
> > Cheers
> > Latif
> >
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