# necessary packages

from matplotlib import pyplot as plt
import numpy as np

# input the data

left_points = [2, 3] # -1 class
right_points = [6, 6.5, 8.3] # +1 class

# graphing parameters

font = {'size':16}
tickfont = {'size':10}
marker_style = dict(linestyle = 'none', markersize = 10, markeredgecolor = 'k')
plt.rcParams['savefig.facecolor'] = '#c0c0c0'

# set up the axes and ticks

fig, ax = plt.subplots()
ax.set_aspect(1)
ax.annotate('', xy = (10, 0), xytext = (-.05, 0),
	arrowprops = {'arrowstyle':'->, head_width = 0.2', 'lw':1,
	'facecolor':'k'}, va = 'center', zorder = -1, **font) 
ax.annotate('$x$', xy = (10.2, 0), xytext = (10.2, 0), va = 'center', **font) 
ax.annotate('', xy = (0, 1.7), xytext = (0, -1.7),
	arrowprops = {'arrowstyle':'-', 'lw':1, 'facecolor':'k'},
	va = 'center')
plt.xticks(np.arange(2, 9, 2), **tickfont)

# plot the data

ax.plot(left_points, np.zeros(len(left_points)), marker = "^",
	markerfacecolor = 'red', **marker_style, label = '$-1$')
ax.plot(right_points, np.zeros(len(right_points)), marker = "s",
	markerfacecolor = 'blue', **marker_style, label='$+1$')
ax.legend(loc = (0.75, 0.65), edgecolor = 'k', facecolor = 'None')

# arrange the axes and box	

plt.gca().axes.get_yaxis().set_visible(False)
plt.box(on = None)
ax.spines['bottom'].set_position('zero')
ax.spines['bottom'].set_color('none')
plt.xlim([-1, 11])
plt.ylim([-2.2, 2.6])

# save the results

fig.savefig('graph.png', bbox_inches = 'tight', pad_inches = -0.1)
plt.show()