[yt-users] Problem with making SlicePlot and ProjectionPlot from new derived field

[Nathan Goldbaum]

Hi Tazkera,

Maybe you want to use units_override, which will let you specify units for
your data if the ones yt infers from the output file are wrong for some
reason:

http://yt-project.org/doc/analyzing/units/comoving_units_and_code_units.html#Overriding-Code-Unit-Definitions

That will let you avoid all of these ad-hoc unit conversions and work
inside the unit system.

Nathan

On Thu, Oct 5, 2017 at 4:59 PM tazkera haque <h.tazkera at gmail.com> wrote:

> Dear yt people,
>
> I am working on a tipsy output file from a n-body simulation. My file
> contains some scaled units for fields like density, coordinates, mass etc.
> To make a physical sense of the data, I had to convert those fields units
> to some physical units (c.g.s) and I derived new fields having cgs unit.
> for example:
>
>
>
>
>
>
>
> *dd = ds.all_data()# derive a new domain width with conversion factor
> (6Mpc*current_time/hubble_constant) def _NewDomainWidth(field, data):
> return
> ds.domain_width*((3.086e18*6e6*0.909090893796)/(0.7))ds.add_field(('gas',
> 'PhysicalDomainWidth'), function=_NewDomainWidth, units="code_length")*
>
>
>
>
>
> *# derive a new domain center with conversion factor
> (6Mpc*current_time/hubble_constant) def _NewDomainCenter(field, data):
> return
> ds.domain_center*((3.086e18*6e6*0.909090893796)/(0.7))ds.add_field(('gas',
> 'PhysicalDomainCenter'), function=_NewDomainCenter, units="code_length")*
>
> note that here "code_length" is actually in "cm". but I could not just do
> dd["Gas",'Coordinates'].in_units('cm'), because this conversion does not
> take into account some constant corrections and returns the wrong length
> magnitude.
>
> My goal was to make sliceplot and  projectionplot of a newly derived field
> :
>
>
>
>
>
>
>
>
> *# derive a new electron pressure fielddef _ElectronPressure(field,
> data):    return
> data['Gas','Density']*(5.49e-7)*data['Gas','Temperature']ds.add_field(('gas',
> 'ElectronPressure'), function=_ElectronPressure,
> units="(code_mass*K)/(code_length**3)")*
>
> *# integration of pressure field along line of sight*
>
> *yt.ProjectionPlot(ds, 'z', ('gas', 'ElectronPressure'), width = dd['gas',
> 'PhysicalDomainWidth'],                   center = dd['gas',
> 'PhysicalDomainCenter'] )*
>
>
> *and it is returning me *
>
> ValueError                                Traceback (most recent call last)<ipython-input-8-fa351b6c09d1> in <module>()      1 yt.ProjectionPlot(ds, 'z', ('gas', 'ElectronPressure'), width = dd['gas', 'PhysicalDomainWidth'], ----> 2                   center = dd['gas', 'PhysicalDomainCenter'] )
>
> ValueError: operands could not be broadcast together with shapes (39678,) (54608,)
>
> Now I cannot use width =ds.domain_width and center = ds.domain_center for the same unit error. I was wondering how I can make the projectionplot for my newly derived field and newly derived domain width and domain center.
>
>
>
> Your suggestion is most welcome
>
>
> Best
>
> Tazkera
>
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