There's more...

Here is another example of using a mix of centimeters and inches on the x and y axis. We have four bar plots with the same input data, plotted on a 2 x 2 grid.

Import the required libraries:

import numpy as np
from basic_units import cm, inch
import matplotlib.pyplot as plt

The following code plots the figure with four bar plots in a 2 x 2 grid:

1. Define the data and the units of measurement:

cms = cm * np.arange(0, 21, 3)
bottom = 0 * cm
width = 0.8 * cm

2. Define the figure and its layout:

fig, axs = plt.subplots(2, 2)

3. Plot a bar chart on the first axes, and set xticks in centimeters:

axs[0, 0].bar(cms, cms, bottom=bottom)
axs[0, 0].set_xticks(cm * np.arange(0, 21, 3))

4. Plot a bar chart on the second axes with the x axis in centimeters and the y axis in inches:

axs[0, 1].bar(cms, cms, bottom=bottom, width=width, xunits=cm, 
              yunits=inch)
axs[0, 1].set_xticks(cm * np.arange(0, 21, 3))

5. Plot a bar chart on the third axes with the x axis in inches and the y axis in centimeters:

axs[1, 0].bar(cms, cms, bottom=bottom, width=width, xunits=inch, 
              yunits=cm)
axs[1, 0].set_xticks(cm * np.arange(0, 21, 3))
axs[1, 0].set_xlim(2, 6) 

6. Plot a bar chart on the fourth axes with both the x and the y axis in inches:

axs[1, 1].bar(cms, cms, bottom=bottom, width=width, xunits=inch, 
              yunits=inch)
axs[1, 1].set_xticks(cm * np.arange(0, 21, 3))
axs[1, 1].set_xlim(2 * cm, 6 * cm) 

7. Adjust the space between the plots and display the figure on the screen:

fig.tight_layout()
plt.show()

Here is the explanation of how it works:

• Prepare the input data for both the x and the y coordinates, set the bottom offset for the bars, and the width of the bar.
• fig, axs = plt.subplots(2, 2) defines the figure layout in a 2 x 2 grid.
• axs[0, 0].bar(cms, cms, bottom=bottom) plots a bar plot on axs[0, 0] and the input data is in centimeters. axs[0, 0].set_xticks(cm * np.arange(0, 21, 3)) sets the tick lines on the x axis so that they are aligned with the bars.
• The bar plot on axs[0, 1] is exactly same as axs[0, 0], except that the units for the y axis changed from centimeters to inches, which is visible on the plot.
• The bar plot on axs[1, 0] is again similar to the one on axs[0, 0], but the units on the x axis changed to inches, and axs[1, 0].set_xlim(2, 6) sets the x axis limits to be (2, 6). Here, only scalars are used to set the limits, without any unit of measurement, which means whatever the x axis unit of measurement is, the same would be applicable for the limits, which in this case range from two to six inches.
• The bar plot on axs[1,1] uses inches as the unit of measurement for both the x and the y axis and sets the x axis limits in centimeters (2, 6), which will be converted to inches in alignment with the unit of measurement for the x axis. So it would be converted to inches, which in this case translates to 0.79 to 2.362 inches.

You should see a figure like the following: