# Graphing tan in matplotlib

I have the following code:

``````from mpl_toolkits.axes_grid.axislines import SubplotZero
from matplotlib.transforms import BlendedGenericTransform
import matplotlib.pyplot as plt
import numpy

if 1:
fig = plt.figure(1)
ax = SubplotZero(fig, 111)

ax.axhline(linewidth=1.7, color="black")
ax.axvline(linewidth=1.7, color="black")

plt.xticks([1])
plt.yticks([])

ax.text(0, 1.05, 'y', transform=BlendedGenericTransform(ax.transData, ax.transAxes), ha='center')
ax.text(1.05, 0, 'x', transform=BlendedGenericTransform(ax.transAxes, ax.transData), va='center')

for direction in ["xzero", "yzero"]:
ax.axis[direction].set_axisline_style("-|>")
ax.axis[direction].set_visible(True)

for direction in ["left", "right", "bottom", "top"]:
ax.axis[direction].set_visible(False)

x = numpy.linspace(-1, 1, 10000)
ax.plot(x, numpy.tan(2*(x - numpy.pi/2)), linewidth=1.2, color="black")

plt.ylim(-5, 5)
plt.savefig('graph.png')
``````

which produces this graph:

As you can see, not only is the tan graph sketched, but a portion of line is added to join the asymptotic regions of the tan graph, where an asymptote would normally be.

Is there some built in way to skip that section? Or will I graph separate disjoint domains of tan that are bounded by asymptotes (if you get what I mean)?

Something you could try: set a finite threshold and modify your function to provide non-finite values after those points. Practical code modification:

``````yy = numpy.tan(2*(x - numpy.pi/2))
threshold = 10000
yy[yy>threshold] = numpy.inf
yy[yy<-threshold] = numpy.inf
ax.plot(x, yy, linewidth=1.2, color="black")
``````

Results in: