I think there is a bigger problem here.
When you do a profile of a field (with some weight field), the values you
get out are the weight-average of the field such that:
profile (field, weight_field) = Sum (field * weight_field) /
Sum(weight_field)
You are comparing
profile(H2_Density) / profile(Density)
with
profile(H2_Density / Density)
Mathematically, these are not the same.
Or, in other words:
mean(x * y) != mean(x) * mean(y)
On Mon, Jan 27, 2014 at 5:24 PM, Stefano Bovino
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
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
wrote: Hi Guys, I did a simple test with enzo and I tried to plot a radial profile of
chemical species fractions with YT.
The problem is that if I use the YT function which intrinsically plot
fraction for a species, let's say H2I_Fraction (as usual), and compare
On Mon, Jan 27, 2014 at 12:14 PM, poetaste@gmail.com
wrote: the the 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_______________________________________________ yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
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