# -*- coding: utf-8 -*-
#from __future__ import unicode_literals
#import matplotlib.pyplot as plt
#from sympy import symbols, sqrt
#from sympy.plotting import plot

#http://www.scipy-lectures.org/intro/matplotlib/matplotlib.html

import numpy as np
import matplotlib.pyplot as plt

plt.rc('text', usetex=True)
plt.rc('font', family='serif')

x = np.linspace(-10, 30, 400, endpoint=True)


def f(x):
    with np.errstate(divide='ignore', invalid='ignore'):
        return np.divide(7,(9-x))

y=f(x)

#plt.plot(X, C)

plt.figure(figsize=(9, 6), dpi=600)
plt.ylim(-25, 25)
# plt.xlim(x.min() * 1.1, x.max() * 1.1)
#
ax = plt.gca()  # gca stands for 'get current axis'
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')
ax.xaxis.set_ticks_position('bottom')
ax.spines['bottom'].set_position(('data',0))
ax.yaxis.set_ticks_position('left')
ax.spines['left'].set_position(('data',0))
#
# #x
# plt.arrow(8.5, -0.003, 0.1, 0, head_width=0.1, head_length=0.25,clip_on=False) #width=0.015, color="k", clip_on=False, head_width=0.12, head_length=0.22)
#
# #y
# plt.arrow(0.0, 8.7, 0, 0.1, clip_on=False, head_width=0.1, head_length=0.25)
#
#
plt.yticks([2,4,6,8])
plt.xticks([-10,-8,-6,-4,-2,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30])#),rotation='vertical')
#
# plt.margins(0.2)
#
#
plt.plot(x, y, color="slateblue")
#
# plt.title(r"$\displaystyle y=f\left(t\right)=\frac{7}{9-t}$" ,fontsize=12, color='slateblue',y=0.15,x=0.3)

plt.savefig('plot07a.pdf', dpi=600)
#plt.show()
#graph.save('plot06a.png')