Dear all, 

I tried to inspect the magnetic field profile in one snap of my enzo output with the code: 

#############################################

from yt.mods import * # set up our namespace

import numpy as np

import pylab as P

def _BMag(field, data):

    return np.sqrt(data["Bx"] * data["Bx"] + data["By"] * data["By"] + data["Bz"] * data["Bz"])

    add_field("BMag", function=_BMag)


    c = pf.h.find_max('BMag')[1]

    ax = 0

    ray = pf.h.ortho_ray(ax, (c[1], c[2]))

   

    P.subplot(212)

    P.semilogy(ray['x'], ray['BMag'])

    P.xlabel('x')

    P.ylabel('BMag')

    print "works"

    P.savefig("BMag_lineplot.png")

#############################################

But keep getting this error message. 

#############################################

(yt-x86_64)[yd742@ria run5]$ python ytplots_BMag_lineplot_dai.py

yt : [INFO     ] 2016-03-12 19:19:31,279 Parameters: current_time              = 0

yt : [INFO     ] 2016-03-12 19:19:31,279 Parameters: domain_dimensions         = [128  64  64]

yt : [INFO     ] 2016-03-12 19:19:31,279 Parameters: domain_left_edge          = [-6000. -3000. -3000.]

yt : [INFO     ] 2016-03-12 19:19:31,280 Parameters: domain_right_edge         = [ 6000.  3000.  3000.]

yt : [INFO     ] 2016-03-12 19:19:31,280 Parameters: cosmological_simulation   = 0.0

Parsing Hierarchy 100% ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| Time: 00:00:00 

yt : [INFO     ] 2016-03-12 19:19:31,285 Gathering a field list (this may take a moment.)

yt : [INFO     ] 2016-03-12 19:19:31,290 Adding unknown field Phi to list of fields

yt : [INFO     ] 2016-03-12 19:19:31,290 Adding unknown field B_Vorticity2 to list of fields

yt : [INFO     ] 2016-03-12 19:19:31,290 Adding unknown field B_Vorticity3 to list of fields

yt : [INFO     ] 2016-03-12 19:19:31,290 Adding unknown field B_Vorticity1 to list of fields

yt : [INFO     ] 2016-03-12 19:19:31,290 Adding unknown field B_Div to list of fields

yt : [INFO     ] 2016-03-12 19:19:32,705 Max Value is 8.56382e-05 at -2501.9531250000000000 29.2968750000000000 228.5156250000000000 in grid EnzoGrid_0005 at level 3 (16, 16, 15)

yt : [INFO     ] 2016-03-12 19:19:32,705 Getting field x from 4

Traceback (most recent call last):

  File "ytplots_BMag_lineplot_dai.py", line 45, in <module>

    P.subplot(212)

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/site-packages/matplotlib-1.3.0-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 896, in subplot

    fig = gcf()

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/site-packages/matplotlib-1.3.0-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 450, in gcf

    return figure()

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/site-packages/matplotlib-1.3.0-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 423, in figure

    **kwargs)

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/site-packages/matplotlib-1.3.0-py2.7-linux-x86_64.egg/matplotlib/backends/backend_tkagg.py", line 79, in new_figure_manager

    return new_figure_manager_given_figure(num, figure)

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/site-packages/matplotlib-1.3.0-py2.7-linux-x86_64.egg/matplotlib/backends/backend_tkagg.py", line 87, in new_figure_manager_given_figure

    window = Tk.Tk()

  File "/home/yd742/software/withpysci/yt-x86_64/lib/python2.7/lib-tk/Tkinter.py", line 1745, in __init__

    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)

_tkinter.TclError: no display name and no $DISPLAY environment variable

#############################################

I'm using yt

Version = 2.6.1

Changeset = c994959ed3be

=======================

I would very much appreciate it if anyone could help me on this. 

Thank you so much. 

Regards, 

Dai