CODEWITHSUNDEEP
pythonmatplotlibplot
Echan
Echan

Reputation: 1415

Adjust spacing on X-axis in python boxplots

I plot boxplots using sns.boxplot and pandas.DataFrame.boxplot in python 3.x.

And I want to ask is it possible to adjust the spacing between boxes in boxplot, so the box of Group_b is farther right to the box of Group_a than in the output figures. Thanks

Codes:

import pandas as pd
import matplotlib.pyplot as plt
%matplotlib inline
import seaborn as sns

dict_a = {'value':[1,2,3,7,8,9],'name':['Group_a']*3+['Group_b']*3}
dataframe = pd.DataFrame(dict_a)
sns.boxplot( y="value" , x="name" , data=dataframe )

Output figure:

enter image description here

dataframe.boxplot("value" ,by = "name" )

Output figure 2:

enter image description here

Upvotes: 4

Views: 7422

Answers (1)

ImportanceOfBeingErnest
ImportanceOfBeingErnest

Reputation: 339170

The distance between the two boxes is determined by the x axis limits. For a constant distance in data units between the boxes, what makes them spaced more or less appart is the fraction of this data unit distance compared to the overall data space shown on the axis. For example, in the seaborn case, the first box sits at x=0, the second at x=1. The difference is 1 unit. The maximal distance between the two boxplots is hence achieved by setting the x axis limits to those exact limits, 

ax.set_xlim(0, 1)

Of course this will cut half of each box.

enter image description here

So a more useful value would be ax.set_xlim(0-val, 1+val) with val being somewhere in the range of the width of the boxes.

One needs to mention that pandas uses different units. The first box is at x=1, the second at x=2. Hence one would need something like ax.set_xlim(1-val, 2+val).

The following would add a slider to the plot to see the effect of different values.

import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns

dict_a = {'value':[1,2,3,7,8,9],'name':['Group_a']*3+['Group_b']*3}
dataframe = pd.DataFrame(dict_a)

fig, (ax, ax2, ax3) = plt.subplots(nrows=3,
                                   gridspec_kw=dict(height_ratios=[4,4,1], hspace=1))

sns.boxplot( y="value" , x="name" , data=dataframe, width=0.1, ax=ax)   
dataframe.boxplot("value", by = "name", ax=ax2)


from matplotlib.widgets import Slider
slider = Slider(ax3, "", valmin=0, valmax=3)

def update(val):
    ax.set_xlim(-val, 1+val)
    ax2.set_xlim(1-val, 2+val)

slider.on_changed(update)


plt.show()

enter image description here

Upvotes: 10

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