Trying to plot a line plot on a bar plot using Matplotlib

Question

I'm trying to plot a line plot over a bar plot using MatPlotLib. So far I have both the plots showing but I can't get a secondary y-axis with a different scale to work. When I try and put another one in it overwrites the original scale. My code is below

def hridef_base(x):
if x == 1:

    deltatlapexit = ExitSummary['Avg tLap'] - ExitSummary2['Avg tLap']

    plt.figure()
    index = (EntrySummary.index + 1)
    barwidth = 0.2

    plt.ylim(0.0, 65.0)
    plt.bar(index-barwidth, EntrySummary['Avg FRH'], barwidth, color='r', yerr=EntrySummary['FRH StDev'], ecolor='k', label='Entry')
    plt.bar(index, ApexSummary['Avg FRH'], barwidth, color='#4169E1', yerr=ApexSummary['FRH StDev'], ecolor='k', label='Apex')
    plt.bar(index+barwidth, ExitSummary['Avg FRH'], barwidth, color='#32CD32', yerr=ExitSummary['FRH StDev'], ecolor='k', label='Exit')

    plt.plot(index, deltatlapexit, color='k', label='Entry')

    plt.xlabel('Turn Number')
    plt.ylabel('Average FRideH')
    plt.title('Average FRideH for Baseline setup')
    plt.xticks(index)
    plt.legend()

else:
    print "Baseline FRideH Not Selected"

Any advice on the matter is appreciated but please talk me through what to do instead of posting links to sites. I need to understand why I'm not able to do this.

Thank-you in advance. Please comment if I've missed anything out.

UPDATE

Thanks to the comments below the graph now has two separate y-axis. How ever the y-label for the bar data has jumped to the right and if I try and plot the line y-label I get an Attribute error.

def hridef_base(x):
if x == 1:

    deltatlapexit = ExitSummary['Avg tLap'] - ExitSummary2['Avg tLap']

    fig, axis1 = subplots()
    index = (EntrySummary.index + 1)
    barwidth = 0.2

    axis1.ylim(0.0, 65.0)
    axis1.bar(index-barwidth, EntrySummary['Avg FRH'], barwidth, color='r', yerr=EntrySummary['FRH StDev'], ecolor='k', label='Entry')
    axis1.bar(index, ApexSummary['Avg FRH'], barwidth, color='#4169E1', yerr=ApexSummary['FRH StDev'], ecolor='k', label='Apex')
    axis1.bar(index+barwidth, ExitSummary['Avg FRH'], barwidth, color='#32CD32', yerr=ExitSummary['FRH StDev'], ecolor='k', label='Exit')

    axis2 = axis1.twinx()
    axis2.set_ylim(-10.0, 10.0)
    axis2.plot(index, deltatlapexit, color='k', label='tDelta')

    axis1.xlabel('Turn Number')
    axis1.ylabel('Average FRideH')
    axis2.set_ylabel('tDelta')
    axis1.title('Average FRideH for Baseline setup')
    axis1.xticks(index)
    axis1.legend()
    axis2.legend()

else:
    print "Baseline FRideH Not Selected"

I would insert an image but I need 10 rep points...

The error I receive is: NameError: global name 'subplots' is not defined

Answer 1

I don't have your data, but using the barplot example from matplotlib, here's an example with a bar plot and a line plot overplotted, with independently scaled y-axes:

from matplotlib import pyplot as plt
import numpy as np

plt.figure()          
N = 5
menMeans = (20, 35, 30, 35, 27)
menStd = (2, 3, 4, 1, 2)
width = 0.35       # the width of the bars
womenMeans = (25, 32, 34, 20, 25)
womenStd = (3, 5, 2, 3, 3)    
ind = np.arange(N)
plt.ylim(0.0, 65.0)
plt.bar(ind, menMeans, width, color='r', yerr=menStd, label='Men means')
plt.bar(ind+width, womenMeans, width, color='y', yerr=womenStd, label='Women means')
plt.ylabel('Bar plot')      

x = np.linspace(0, N)
y = np.sin(x)
axes2 = plt.twinx()
axes2.plot(x, y, color='k', label='Sine')
axes2.set_ylim(-1, 1)
axes2.set_ylabel('Line plot')

plt.show()