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Comments on How to add vertical lines for visual separation in pandas plot

Parent

How to add vertical lines for visual separation in pandas plot

+3
−0

MWE

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


df = pd.DataFrame(np.random.rand(9, 4), columns=['a', 'b', 'c', 'd'])
df.plot.bar()
plt.show()

Busy Bar Graph

Question

How do I add separating vertical lines between groups? Say these are groups of three:
(0, 1, 2), LINE, (3, 4, 5), LINE, (6, 7, 8)

Notes

This really helps for recognizing patterns and tracking trends in a busy, but useful graph.

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I don't think this is possible using just the Pandas plotting API. You can use the lower-level Matplotlib API to do just about anything you can imagine:

ax = df.plot.bar()
vlines = [2.5, 5.5] # x-positions of the group separators
ax.vlines(vlines, 0, 1,
        transform=ax.get_xaxis_transform(), # [1]
        color='black',
        linewidths=0.8) # [2]
# [1]: This makes the above 0 and 1 refer to the top and bottom
# of the plot, regardless of the actual scale used for the data.
# [2]: 0.8 is the default width used for the axis frame
# (matplotlib.rcParams['axes.linewidth'], if you prefer).
plt.show()

ax here is a Matplotlib Axes object, and you can read about all the things you can do with it here.

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2 comment threads

Because this is so manual, I might consider post-processing in Gimp or similar. (3 comments)
Sounds promising, can you post output? (1 comment)
Because this is so manual, I might consider post-processing in Gimp or similar.
mcp‭ wrote over 2 years ago

Because this is so manual, I might consider post-processing in Gimp or similar.

__blackjack__‭ wrote over 2 years ago

As you mentioned LaTeX in another, similar question, I would recommend against using/saving a pixel image. When you save the figure(s) in PDF or EPS format, they can be included as vector graphic in the LaTeX document to get good quality at any resolution without the need to include very high resolution pixel images.