python - Error with matplotlib when running exmaples of scikit learn -

i learning python, , came across package called scikit learn can use python libraries , custom made codes generate various plots. have installed dependancies , have downloaded , installed scikit learn when trying run example codes getting error in generating plot.

code

from sklearn import datasets sklearn.cross_validation import cross_val_predict sklearn import linear_model import matplotlib.pyplot plt  lr = linear_model.linearregression() boston = datasets.load_boston() y = boston.target  # cross_val_predict returns array of same size `y` each entry # prediction obtained cross validated: predicted = cross_val_predict(lr, boston.data, y, cv=10)  fig,ax = plt.subplots() ## error comes calling function plt.subplots() ax.scatter(y, predicted) ax.plot([y.min(), y.max()], [y.min(), y.max()], 'k--', lw=4) ax.set_xlabel('measured') ax.set_ylabel('predicted') fig.show() 

error

fig,ax = plt.subplots() traceback (most recent call last):   file "<stdin>", line 1, in <module>   file "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 866, in subplots     fig = figure(**fig_kw)   file "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 343, in figure     **kwargs)   file "/usr/lib/pymodules/python2.7/matplotlib/backends/backend_tkagg.py", line 80, in new_figure_manager     window = tk.tk()   file "/usr/lib/python2.7/lib-tk/tkinter.py", line 1712, in __init__     self.tk = _tkinter.create(screenname, basename, classname, interactive, wantobjects, usetk, sync, use) _tkinter.tclerror: no display name , no $display environment variable 

is setting environmental variable? using python 2.7.3 , package should work or doing have put path or something? sorry new python trying figure out if can use package generating plots or not. rid of error appreciated.

i suspect trying run code on distant machine (ssh maybe) or matplotlib not installed.

if in first case, suggest use savefig command matplotlib.use('agg') tells matplotlib not use default display. produce .png file import home using scp:

import matplotlib matplotlib.use('agg') pylab import savefig sklearn import datasets sklearn.cross_validation import cross_val_predict sklearn import linear_model import matplotlib.pyplot plt  lr = linear_model.linearregression() boston = datasets.load_boston() y = boston.target  # cross_val_predict returns array of same size `y` each entry # prediction obtained cross validated: predicted = cross_val_predict(lr, boston.data, y, cv=10)  fig,ax = plt.subplots() ## error comes calling function plt.subplots() ax.scatter(y, predicted) ax.plot([y.min(), y.max()], [y.min(), y.max()], 'k--', lw=4) ax.set_xlabel('measured') ax.set_ylabel('predicted')  # don't use fig.show()  savefig('figure_name.png') # savefig matplotlib