#!/usr/bin/python
# -*- coding: utf8 -*-

import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
from math import *

code_website = 'http://commons.wikimedia.org/wiki/User:Geek3/mplwp'
try:
    import mplwp
except ImportError, er:
    print 'ImportError:', er
    print 'You need to download mplwp.py from', code_website
    exit(1)

name = 'mplwp_sgn.svg'
fig = mplwp.fig_standard(mpl)

xlim = -3,3; fig.gca().set_xlim(xlim)
ylim = -2,2; fig.gca().set_ylim(ylim)
fig.gca().yaxis.set_major_locator(mpl.ticker.MultipleLocator(1))
mplwp.mark_axeszero(fig.gca())

l = plt.plot([xlim[0], -4.8/515*6, float('NAN'), 4.8/515*6, xlim[1]],
         [-1, -1, float('NAN'), 1, 1], label=r'sgn(x)')
col = l[0].get_color()
plt.plot([0], [0], 'o', markeredgewidth=1.8,
         markerfacecolor=col, markeredgecolor=col)
plt.plot([0, 0], [-1, 1], 'o', markeredgewidth=1.8,
         markerfacecolor='none', markeredgecolor=col)

plt.legend(loc='upper center').get_frame().set_alpha(0.9)
plt.savefig(name)
mplwp.postprocess(name)