Plotting multiple bars with matplotlib using ax.bar()

Question

Following up my previous question: Sorting datetime objects by hour to a pandas dataframe then visualize to histogram

I need to plot 3 bars for one X-axis value representing viewer counts. Now they show those under one minute and above. I need one showing the overall viewers. I have the Dataframe but I can't seem to make them look right. With just 2 bars I have no problem, it looks just like I would want it with two bars:

The relevant part of the code for this:

# Time and date stamp variables
allviews = int(df['time'].dt.hour.count())
date = str(df['date'][0].date())
hours = df_hist_short.index.tolist()
hours[:] = [str(x) + ':00' for x in hours]

The hours variable that I use to represent the X-axis may be problematic, since I convert it to string so I can make the hours look like 23:00 instead of just the pandas index output 23 etc. I have seen examples where people add or subtract values from the X to change the bars position.

fig, ax = plt.subplots(figsize=(20, 5))
short_viewers = ax.bar(hours, df_hist_short['time'], width=-0.35, align='edge')
long_viewers = ax.bar(hours, df_hist_long['time'], width=0.35, align='edge')

Now I set the align='edge' and the two width values are absolutes and negatives. But I have no idea how to make it look right with 3 bars. I didn't find any positioning arguments for the bars. Also I have tried to work with the plt.hist() but I couldn't get the same output as with the plt.bar() function.

So as a result I wish to have a 3rd bar on the graph shown above on the left side, a bit wider than the other two.

Answer 1

pandas will do this alignment for you, if you make the bar plot in one step rather than two (or three). Consider this example (adapted from the docs to add a third bar for each animal).

import pandas as pd
import matplotlib.pyplot as plt

speed = [0.1, 17.5, 40, 48, 52, 69, 88]
lifespan = [2, 8, 70, 1.5, 25, 12, 28]
height = [1, 5, 20, 3, 30, 6, 10]
index = ['snail', 'pig', 'elephant',
         'rabbit', 'giraffe', 'coyote', 'horse']
df = pd.DataFrame({'speed': speed,
                   'lifespan': lifespan,
                   'height': height}, index=index)
ax = df.plot.bar(rot=0)

plt.show()