Hi Sushil,

I think what you need to do is to assign the correct field name when loading the data. In your script, you have:

data = dict(field1 = field1,
            field2 = field2,
            field3 = field3)

which could be, say,

data = dict(magnetic_field_x = field1,
            magnetic_field_y = field2,
            magnetic_field_z = field3)

since annotate_magnetic_field will directly refer to these field names (in fact it's a specialized version of annotate_quiver).

Best wishes,
--
Suoqing JI
Ph.D Candidate
Department of Physics
University of California, Santa Barbara

On Mar 16, 2016, at 12:16 PM, Sushilkumar <sushil.sush19us@gmail.com> wrote:

Dear yt:

I am trying to plot magnetic field lines using the annotate magnetic field call back from the link http://yt-project.org/doc/visualizing/callbacks.html link.

However, after running the script it gives the error below. A google drive link to my script (yt_numpy_load_B.py) is also given below. When I use quiver annotate it works fine but issue comes when I am using slc.annotate_magnetic_field().
Quiver plots are also available on the drive link.

Thanks in advance

===============
Google drive link
https://drive.google.com/open?id=0B4g8shg4DL7oak5PLWVVdG5UMHc
===============

===============
Error while running the script

  File "yt_numpy_load_B.py", line 47, in <module>
    slc.save()
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_container.py", line 77, in newfunc
    args[0]._setup_plots()
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_window.py", line 980, in _setup_plots
    self.run_callbacks()
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_window.py", line 1033, in run_callbacks
    sys.exc_info()[2])
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_window.py", line 1029, in run_callbacks
    callback(cbw)
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_modifications.py", line 316, in __call__
    return qcb(plot)
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/visualization/plot_modifications.py", line 357, in __call__
    fv_x = plot.data[self.field_x]
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/data_objects/data_containers.py", line 246, in __getitem__
    f = self._determine_fields([key])[0]
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/data_objects/data_containers.py", line 518, in _determine_fields
    finfo = self.ds._get_field_info("unknown", fname)
  File "/state/partition1/anaconda/lib/python2.7/site-packages/yt/data_objects/static_output.py", line 543, in _get_field_info
    raise YTFieldNotFound((ftype, fname), self)
yt.utilities.exceptions.YTPlotCallbackError: annotate_magnetic_field callback failed with the following error: Could not find field '('all', 'magnetic_field_x')' in UniformGridData.
===============




On Wed, Mar 16, 2016 at 12:52 PM, <yt-users-request@lists.spacepope.org> wrote:
Send yt-users mailing list submissions to
        yt-users@lists.spacepope.org

To subscribe or unsubscribe via the World Wide Web, visit
        http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
or, via email, send a message with subject or body 'help' to
        yt-users-request@lists.spacepope.org

You can reach the person managing the list at
        yt-users-owner@lists.spacepope.org

When replying, please edit your Subject line so it is more specific
than "Re: Contents of yt-users digest..."


Today's Topics:

   1. Re: Making averaged line plot. (Suoqing Ji)


----------------------------------------------------------------------

Message: 1
Date: Tue, 15 Mar 2016 15:23:43 -0700
From: Suoqing Ji <suoqing@physics.ucsb.edu>
To: Discussion of the yt analysis package
        <yt-users@lists.spacepope.org>
Subject: Re: [yt-users] Making averaged line plot.
Message-ID: <70E5BA6C-7798-45F2-AE83-21233252E109@physics.ucsb.edu>
Content-Type: text/plain; charset="utf-8"

Hi Yuxiao,

If you would like to start from your current code, the most straightforward way is to write a loop to smooth over a certain distance by each step, which also works for AMR data:

smooth_len = 100 # smoothing length of 100 kpc
SmoothedBMag = np.copy(ray[?ScaledBMag?]) # store the smoothed array
bin_num = np.ceiling((ray[?x?].max() - ray[?x?].min()) / smooth_len) # make bins every 100 kpc

for step in range(bin_num):
    mask1 = (ray[?x?] >= ray[?x?].min() + step * smooth_len)
    mask2 = (ray[?x?] < ray[?x?].min() + (step + 1) * smooth_len)
    mask = np.logical_and(mask1, mask2) # mask the cells within a certain length of 100 kpc
    SmoothedBMag[mask] = np.mean(ray[?ScaledBMag?][mask]) # take the average and save

After that the array ?SmoothedBMag? is the smoothed one.

However, an easier way is to use the the 1D ProfilePlot function (http://yt-project.org/docs/2.6/visualizing/plots.html#d-profile-plots <http://yt-project.org/docs/2.6/visualizing/plots.html#d-profile-plots>), and in this case you could do something like:

plot = ProfilePlot(pf.h.all_data(), ?x?, [?ScaledBMag?], n_bins=bin_num)

Note that this will do the average over entire y-z plane for each x bins, which is different from averaging only an array of a ray object (so maybe it?s not what you want). If you really want the data within a thin slit only, you could define a region object pf.h.region() and do ProfilePlot. I think it?s also doable to use the function ?load_uniform_grid? to create a 1D dataset from the arrays in ray object and pass it to ProfilePlot.

Best wishes,
--
Suoqing JI
Ph.D Candidate
Department of Physics
University of California, Santa Barbara
http://web.physics.ucsb.edu/~suoqing

> On Mar 14, 2016, at 10:57 PM, Yuxiao Dai <yuxiao.dai@nyu.edu> wrote:
>
> Dear all,
>
> I have a line plot of some parameter along an axis as a function of distance. Now I would like to get another line plot of the same parameter but averaged over a certain distance (say 100 kpc, the plot below is supposed to be flat after this). I've been searching the document for some time but haven't found a method. Is there a simple way to do this?
>
> I would very much appreciate it if anyone could help me on this.
>
>
> ===================================
> import ...
>
> def _ScaledBMag(field, data):
>
>     return ...
>
>
>
> ....
>
> pf = load(filename)
>
>     add_field("ScaledBMag", function=_ScaledBMag)
>
>
>
>     c = pf.h.find_max('ScaledBMag')[1]
>
>     ax = 0
>
>     ray = pf.h.ortho_ray(ax, (c[1], c[2]))
>
>
>     P.subplot(211)
>
>     P.semilogy(ray['x'], ray['ScaledBMag'])
>
>     P.xlabel('x')
>
>     P.ylabel('ScaledBMag')
>
>     print "works"
>
>     P.savefig("ScaledBMag_lineplot.png")
>
>
> <image.png>
>
> ===================================
> I'm using yt
>
> Version = 2.6.1
>
>
> Changeset = c994959ed3be
>
> ===================================
>
>
>
>
>
> Regards,
>
> Dai
>
> _______________________________________________
> yt-users mailing list
> yt-users@lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-users-spacepope.org/attachments/20160315/8afc239c/attachment.html>

------------------------------

Subject: Digest Footer

_______________________________________________
yt-users mailing list
yt-users@lists.spacepope.org
http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org


------------------------------

End of yt-users Digest, Vol 97, Issue 19
****************************************



--
SK2

"Claiming that something can move faster than light is a good conversation-stopper in physics. People edge away from you in cocktail parties; friends never return phone calls. You just don’t mess with Albert Einstein."

_______________________________________________
yt-users mailing list
yt-users@lists.spacepope.org
http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org