ah... I'm binning, it also depends on the number of bins I'm using, but the discrepancy (slight) is still there):

prof3 = BinnedProfile1D(sph3, 64, "Radiuspc", 1.0e-6, 1.0e6)

In my initial setup I'm using a box of 300 pc.

Stefano


On Mon, Jan 27, 2014 at 6:20 PM, Stefano Bovino <poetaste@gmail.com> wrote:
Hi Matt,
thanks for the quick reply.
I'm using simple data from the enzo Collapse Test (27).
It seems is mainly related to the size of the sphere I'm taking... but I don't know.

Here following a piece of my script:

 pf3=load("DD0003/DD0003")
c3= pf3.h.find_max("Density")[1]
sph3 = pf3.h.sphere(c3, (100, 'pc'))
prof3.add_fields("H2I_Density")
prof3.add_fields("H2I_Fraction")
prof3.add_fields("Radius")

...
...

d_ax2.loglog(prof3['Radius'], prof3['H2I_Density']/prof3['Density'],
            lw=1.5, linestyle='--', color='r')
d_ax2.loglog(prof3['Radius'], prof3['H2I_Fraction'],
            lw=1.5, linestyle=':', color='y')

Thanks in advance
Stefano


On Mon, Jan 27, 2014 at 6:11 PM, Matthew Turk <matthewturk@gmail.com> wrote:
On Mon, Jan 27, 2014 at 12:14 PM, poetaste@gmail.com <poetaste@gmail.com> wrote:
> Hi Guys,
> I did a simple test with enzo and I tried to plot a radial profile of the
> chemical species fractions with YT.
>
> The problem is that if I use the YT function which intrinsically plot the
> fraction for a species, let's say H2I_Fraction (as usual), and compare this
> with a direct evaluation of the mass fraction:
>
> data['H2I_Density']/data['Density']
>
> I obtain some slightly different results, mostly at large radii.
>
> Anyone might explain this discrepancy!? This happens with all the species.

Without knowing what "data" here is, or how you generated it, it's tough to say.

-Matt

>
> Thank you in advance
> Stefano_______________________________________________
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> yt-users@lists.spacepope.org
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