Plotting mulitple lines on two y axis using Matplotlib

Question

I am trying to plot multiple features which have different ranges on two y axis. Each axis might contain more than one feature. Code snippet below includes object "Prin Balances" which is a df which contains datatypes float indexed by dates. "Delinquent States" is a list containing a subset of the column headers of Prin Balances.

Delinquent_States = ['1 Mos','2 Mos','3 Mos','> 3 Mos']
fig, ax = plt.subplots()
plt.plot(Prin_Balances['UPB'], '--r', label='UPB')
plt.legend()
ax.tick_params('Bal', colors='r')

# Get second axis
ax2 = ax.twinx()
plt.plot(Prin_Balances[Delinquent_States],  label=Delinquent_States)
plt.legend()
ax.tick_params('vals', colors='b')

My output needs to be cleaned up, esp the legends.

Any suggestions welcomed.

You can plot it all in one image, but the lines from 0 to 0.05 will of course be too much far from the others. Best way is to plot two subplots. — Vinícius Figueiredo
– Vinícius Figueiredo, Commented Jul 18, 2017 at 0:26

Carlo Mazzaferro · Accepted Answer · 2017-07-18 15:46:13Z

15

As simple as:

import pandas
import matplotlib.pyplot as plt
import random

# Generate some random data
df = pandas.DataFrame({'a': [random.uniform(0,0.05) for i in range(15)], 
                       'b': [random.uniform(0,0.05) for i in range(15)], 
                       'c': [random.uniform(0.8,1) for i in range(15)],
                       'd': [random.uniform(0.8, 1) for i in range(15)],
                       'e': [random.uniform(0.8, 1) for i in range(15)]})
plt.plot(df)

Returns:

I would suggest however plotting them separately:

fig, ax = plt.subplots(nrows=2,ncols=1)
plt.subplot(2,1,1)
plt.plot(df['a'], 'r', label='Line a')
plt.legend()

plt.subplot(2,1,2)
plt.plot(df['b'], 'b', label='Line b')
plt.legend()

Which yelds:

ADDED:

You can set different scales for each side of the plot:

fig, ax = plt.subplots()
plt.plot(df['a'], '--r', label='Line a')
plt.plot(df['b'], '--k', label='Line b')
plt.legend()
ax.tick_params('vals', colors='r')

# Get second axis
ax2 = ax.twinx()
plt.plot(df['c'], '--b', label='Line c')
plt.plot(df['d'], '--g', label='Line d')
plt.plot(df['e'], '--c', label='Line e')
plt.legend()
ax.tick_params('vals', colors='b')

Not the prettiest, but you get the point.

edited Jul 18, 2017 at 15:46

answered Jul 18, 2017 at 0:31

Carlo Mazzaferro

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7 Comments

GPB Over a year ago

Yes, but how to plot multiple lines with different ranges (per my question) on the same graph with 2 axis? Your examples are useful but do not answer my question - unless I am missing something?

Carlo Mazzaferro Over a year ago

There you go. See if this is what you are looking for @GPB

GPB Over a year ago

Almost - how do I plot multiple lines with different colours on each axis?

Carlo Mazzaferro Over a year ago

Well, isn't that what the code is doing? Each axis refers to a line. The red line is scaled according to the left-most axis, and the blue line is scaled according to the right-most axis.

GPB Over a year ago

I take it your question is rhetorical? :-). I've added an update to my question, I cannot figure out how to use a list to label the legend for multiple lines.

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