This is an issue with matplotlib. When pyplot tries to open a plotting window, it dies because you don't have an X11 server set up (probably because you haven't set up ssh forwarding).

The easiest fix is to tell matplotlib to use the non-interactive agg backend. Add the following to the top of your script:

import matplotlib
matplitlib.use('agg')

-Nathan

On Sat, Mar 12, 2016 at 6:33 PM, Yuxiao Dai <yuxiao.dai@nyu.edu> wrote:

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


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