[yt-users] Related to Off axis plot and Dark matter density field

[Nathan Goldbaum]

On Fri, Oct 14, 2016 at 3:47 AM, Prateek Gupta <prateekgidolia at gmail.com>
wrote:

> Dear Yt users,
>
> I want to the off axis slice plot of density. But I didn't understand the
> use of north_vector. We already gave the normal vector to the plane and the
> point and these two things are enough to write a plane equation. I think I
> am confused with the concept. Please help me in understanding it very well.
>
>
The north_vector is the "up" direction in the image. The normal_vector only
sets the location that the image "looks" at, but not the overall rotation.
Setting north_vector allows you to control the orientation of the image.

If the normal_vector and north_vector are not orthogonal, then in practice
yt uses the component of the north_vector that is perpendicular to the
normal_vector. If normal_vector and north_vector are parallel, an error
will be raised.


>
> I am facing one more problem. I want the dark matter density Sliceplot.
> But when I used the field "dark_matter_density", it's not giving the
> correct plot I think. Here I attach the plot also for your reference.
> (check2.png)
>

It looks like you're looking at a dataset where the dark matter aren't as
well-resolved as other species, which means that there are many cells with
no or very few dark matter particles.

You might find that visualizing your deposited particle fields will work
better on a more coarse mesh, for example a mesh created using an
arbitrary_grid data object:

http://yt-project.org/doc/reference/api/generated/yt.data_objects.construction_data_containers.YTArbitraryGrid.html?highlight=arbitrary_grid
http://yt-project.org/doc/analyzing/objects.html#arbitrary-grids-objects


>
>
> Then I searched and got that it can also be done if I plot the
> particle_density so I define field like this as given in yt-doc.
>
> def particle_density(field, data):
>     pos = data[ptype, coord_name]
>     mass = data[ptype, mass_name]
>     pos.convert_to_units("code_length")
>     mass.convert_to_units("code_mass")
>     d = data.deposit(pos, [data[ptype, mass_name]], method = "sum")
>     d = data.ds.arr(d, "code_mass")
>     d /= data["index", "cell_volume"]
>     return d
>
>
Where in the documentation did this come from? In order to use this field
definition you need to set the 'ptype' variable. If there is a particle
type in your output corresponding to dark matter, use that. If there is
only one particle type in your output, you can create a dark matter
particle type using a particle filter:

http://yt-project.org/doc/analyzing/filtering.html#filtering-particle-fields


> but this also give an error says :
>
>
> *NameError: global name 'ptype' is not defined*
> *but "all_density" field is working fine. *But it will be total density
> (dark + baryon
> *)*
> Please help me regarding this issue.
>
>
>
>
> Thanks in advance.
>
> Prateek Gupta.
>
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