I haven't done the projection, but changed the disk definition to

disk = pf.h.disk([0.0,0.0,0.0][0.0,0.0,1.0],1.2,0.1925)

(more or less what Nathan suggested) and end up with basically the same values for the "Ones" count. 

I thought that in the disk definition the z input was the total height of the cylinder?

-Stephanie

On Mon, Aug 4, 2014 at 2:36 PM, Nathan Goldbaum <nathan12343@gmail.com> wrote:

So tracep25 includes about half of the cells that tdp25 does.

What if you do this instead:

tracerp25 = alld.cut_region(["grid['specific_scalar[0]'] > 0.25","grid['z'] < 0.385","grid['z'] > -0.385","grid['cyl_Rcode'] < 1.2"])

On Mon, Aug 4, 2014 at 11:34 AM, Stephanie Tonnesen <stonnes@gmail.com> wrote:

Hi John,

When I change the tracerp25 selections to all have <= or >= symbols, the value basically doesn't change.  With the gt/lt and equal-to "Ones" is definitely different:

tracerp25 is 1099285

tdp25 is 2028955

So the selection criteria is definitely more stringent on
tracerp25 = alld.cut_region(["grid['

specific_scalar[0]'] > 0.25","grid['z'] <= 0.1925","grid['z'] >= -0.1925","grid['cyl_Rcode'] <= 1.2"])

-Stephanie

On Mon, Aug 4, 2014 at 2:11 PM, John ZuHone <jzuhone@gmail.com> wrote:

Hi Stephanie,

I suspect the problem is that these are not *exactly* the same regions. Have you tried checking the result of:

tdp25["Ones"].sum()

tracerp25["Ones"].sum()

which would be a quick way to determine the number of cells in each region.

What might be going on (but I have yet to verify) is that the disk selection container object is using >= and <= for the zone selection, whereas you used > and < in the definition of your cut region. You might try swapping those out and seeing if that changes things.

Best,

John Z

On Aug 4, 2014, at 1:15 PM, Stephanie Tonnesen <stonnes@gmail.com> wrote:

> Hi all,
>
> I am trying to get the total mass in a disk region of my simulation.  I am using athena data and yt 2.7-dev.  I thought I was defining the region in the same way using two methods:
>
> alld = pf.h.all_data()
> tracerp25 = alld.cut_region(["grid['specific_scalar[0]'] > 0.25","grid['z'] < 0.1925","grid['z'] > -0.1925","grid['cyl_Rcode'] < 1.2"])
>
> disk = pf.h.disk([0.0,0.0,0.0],[0.0,0.0,1.0],1.2,0.385)
> tdp25 = disk.cut_region(["grid['specific_scalar[0]'] > 0.25"])
>
> but when I print the total mass I get answers that differ by 10%
>
> print tracerp25.quantities["TotalQuantity"]("CellMassMsun")
> print tdp25.quantities["TotalQuantity"]("CellMassMsun")
>
> >>[8019047231.5192223]
> >>[8886968784.4710732]
>
> Can someone point out where my difference is?
>
> Thanks!
>
> Stephanie

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