Combining a grouped bar plot with a truncated line chart

Question

I know how to create a grouped bar plot and I know how to create a line plot in matplotlib but unfortunately, I don't know how to combine both in a way that groups the line plots as well according to the bar groups, while preserving two axes. The following sketch (hopefully) illustrates what I try to achieve:

And this is what I have done so far:

import matplotlib
import matplotlib.pyplot as plt
import numpy as np

labels = ['G1', 'G2', 'G3', 'G4', 'G5']
men_means = [20, 34, 30, 35, 27]
women_means = [25, 32, 34, 20, 25]

YearGroup1 = ['G11','G12']
Unemployment_RateGroup1 = [31,32]

x = np.arange(len(labels))  # the label locations
width = 0.35  # the width of the bars

fig, ax = plt.subplots()
rects1 = ax.bar(x - width/2, men_means, width, label='Men')
rects2 = ax.bar(x + width/2, women_means, width, label='Women')

# Add some text for labels, title and custom x-axis tick labels, etc.
ax.set_ylabel('Scores')
ax.set_title('Scores by group and gender')
ax.set_xticks(x)
ax.set_xticklabels(labels)
ax.legend()

def autolabel(rects):
    """Attach a text label above each bar in *rects*, displaying its height."""
    for rect in rects:
        height = rect.get_height()
        ax.annotate('{}'.format(height),
                    xy=(rect.get_x() + rect.get_width() / 2, height),
                    xytext=(0, 3),  # 3 points vertical offset
                    textcoords="offset points",
                    ha='center', va='bottom')

autolabel(rects1)
autolabel(rects2)

fig.tight_layout()

plt.plot(YearGroup1, Unemployment_RateGroup1)
plt.show()

However, I don't know how to reposition the x-positions of the line chart manually. The lines are supposed to be within groups and should be on the second y-axis.

The whole plot aims to show results for different algorithms (X_1,X_2,X_3,...) on different data types (red bar, green bar, blue bar). The grouped line charts on the second y-axis should represent the time needed for each algorithm.

Any help is highly appreciated.

Answer 1

Assuming the line plot is supposed to display within group data, you can plot it like this:

import matplotlib
import matplotlib.pyplot as plt
import numpy as np

labels = ['G1', 'G2', 'G3', 'G4', 'G5']
men_means = [20, 34, 30, 35, 27]
women_means = [25, 32, 34, 20, 25]

YearGroup1 = ['G11','G12']
Unemployment_RateGroup1 = [31,32]

x = np.arange(len(labels))  # the label locations
width = 0.35  # the width of the bars

fig, ax = plt.subplots()
ax2 = ax.twinx()  # <--- make a second y-axis
rects1 = ax.bar(x - width/2, men_means, width, label='Men')
rects2 = ax.bar(x + width/2, women_means, width, label='Women')

# Add some text for labels, title and custom x-axis tick labels, etc.
ax.set_ylabel('Scores')
ax.set_title('Scores by group and gender')
ax.set_xticks(x)
ax.set_xticklabels(labels)
ax.legend()

def autolabel(rects):
    """Attach a text label above each bar in *rects*, displaying its height."""
    for rect in rects:
        height = rect.get_height()
        ax.annotate('{}'.format(height),
                    xy=(rect.get_x() + rect.get_width() / 2, height),
                    xytext=(0, 3),  # 3 points vertical offset
                    textcoords="offset points",
                    ha='center', va='bottom')

autolabel(rects1)
autolabel(rects2)

# plot lines    
for i in range(len(labels)):
    ax2.plot(
        [x[i] - width / 2, x[i] + width / 2], 
        Unemployment_RateGroup1, 
        color='C3', marker='+', mec='k'
    )

fig.tight_layout()

Please mind that I dropped plt.show() . If you require this line, don't forget to add it.

If you have separate data of Unemployment_Rate for each group, fi

Unemployment_Rate = [[31, 32], [7, 12], [23, 9], [0, 1], [32, 0]]

you can replace the line plotting with:

ax2.plot(
    [x[i] - width / 2, x[i] + width / 2], 
    Unemployment_Rate[i], 
    color='C3', marker='+', mec='k'
)

which will yield: