NCL_bar_11.py

This script illustrates the following concepts:

• Drawing filled bars using solid colors

• Setting the minimum/maximum value of the X and Y axis in a bar plot

• Paneling bar plots

• Drawing a custom legend

• Generating random data using numpy

See following URLs to see the reproduced NCL plot & script:

• Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/bar_11.ncl

• Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/bar_11_lg.png

Import packages:

import matplotlib.pyplot as plt
import numpy as np

import geocat.viz as gv

Generate dummy data:

num_months = 12
bars_per_panel = 4
panels = 4
data = np.random.uniform(0.1, 1.15, (panels, bars_per_panel, num_months))

months = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec',
]

Plot:

fig, axs = plt.subplots(2, 2, figsize=(12, 8), gridspec_kw=dict(wspace=0.25))
x = np.arange(len(months))  # where to draw x ticks
width = 0.2  # width of each bar within the groups

# Create the subplots using a loop
panel = 0
for row in range(0, 2):
    for col in range(0, 2):
        # Use geocat.viz.util convenience function to set axes parameters
        gv.set_axes_limits_and_ticks(
            axs[row][col],
            ylim=(0.4, 1.2),
            xticks=x,
            yticks=np.arange(0.4, 1.4, 0.2),
            xticklabels=months,
        )
        # Use geocat.viz.util convenience function to add minor and major tick lines
        gv.add_major_minor_ticks(
            axs[row][col], x_minor_per_major=1, y_minor_per_major=4, labelsize=12
        )
        # Use geocat.viz.util convenience function to set titles and labels
        gv.set_titles_and_labels(axs[row][col], ylabel='(\u00b0C)', labelfontsize=14)

        # Add overall figure title
        fig.suptitle('Paneling bar plots, dummy data', size=20, y=0.94)

        # Add data to subplot
        axs[row][col].bar(
            x - width * 3 / 2,
            data[panel][0][:],
            width,
            edgecolor='black',
            linewidth=0.25,
            color='red',
            label='first',
        )
        axs[row][col].bar(
            x - width / 2,
            data[panel][1][:],
            width,
            edgecolor='black',
            linewidth=0.25,
            color='lightsteelblue',
            label='second',
        )
        axs[row][col].bar(
            x + width / 2,
            data[panel][2][:],
            width,
            edgecolor='black',
            linewidth=0.25,
            color='blue',
            label='third',
        )
        axs[row][col].bar(
            x + width * 3 / 2,
            data[panel][3][:],
            width,
            edgecolor='black',
            linewidth=0.25,
            color='lime',
            label='fourth',
        )
        panel += 1

# Add legend with `figlegend()` to position it relative to figure instead of subplots
handles, labels = axs[0][0].get_legend_handles_labels()
fig.legend(
    handles,
    labels,
    ncol=4,
    loc='lower center',
    fontsize=14,
    columnspacing=5,
    frameon=False,
)

plt.show()