Graphing
Most of the necessary information for learning how to make basic plots in Python is in the IPython notebook, but there are a few tips and tricks that are worth mentioning.
Show
import numpy as np
import matplotlib as plt
x = np.array(range(20))
y = 3 + 0.5 * x + np.random.randn(20)
plt.plot(x, y)
In Python, sometimes, new figures won’t display by default. Python waits until
you tell it to display those figures by using the .show() method in
matplotlib.pyplot. In most environments you should be able to either use
plt.show() as many times as you want, or just at the end of the code, but if
you’re running into problems where only the first graph displays then this can
be fixed by only using a single plt.show() at the end of your code.
New Figures
plt.figure() will start a new figure.
Hold
plt.hold(True)will set the figure to add new data rather than overwriteplt.hold(False)will set the figure to overwrite the existing dataplt.hold()will switch back and forth, but this requires that you know the current state so I prefer explictly usingTrueandFalse.
z = 2 + 0.75 * x + np.random.randn(20)
Making Graphing Easier
Making nice looking graphs can sometimes take a lot of work. There are a couple of modules that make this easier.
import pandas as pd
import seaborn as sns
data = pd.DataFrame(x, columns=["x"])
data["y"] = y
sns.lmplot('x', 'y', data)
plt.show()