NCL_box_2.py

This script illustrates the following concepts:

• Drawing box plots

• Manipulating boxplot visualizations

• Manipulating plot axes

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

• Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/box_2.ncl

• Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/box_2_lg.png

Import packages:

import matplotlib.pyplot as plt
from matplotlib.ticker import FormatStrFormatter
import numpy as np

import geocat.viz as gv

Generate fake data:

seed = 200
np.random.seed(seed)

data = np.random.lognormal(size=(40, 3), mean=1, sigma=0.7)
for a in range(len(data)):
    data[a] = [x - 4 for x in data[a]]

Helper function to set edge color of boxes

def setBoxColor(boxplot, colors):
    # Set edge color of the outside and median lines of the boxes
    for element in ['boxes', 'medians']:
        for box, color in zip(boxplot[element], colors):
            plt.setp(box, color=color)

    # Set the color of the whiskers and caps of the boxes
    for element in ['whiskers', 'caps']:
        for box, color in zip(
            zip(boxplot[element][::2], boxplot[element][1::2]), colors
        ):
            plt.setp(box, color=color)

Plot:

# Create figure and axis
w = 0.1
fig, ax = plt.subplots(figsize=(6, 6))
boxplots = ax.boxplot(
    data, tick_labels=['Control', '-2Xna', '2Xna'], widths=[w, w, w], showfliers=False
)

# Set whiskers style to dashed
plt.setp(boxplots['whiskers'], linestyle='--')

# Set boxplot edge colors
setBoxColor(boxplots, ['blue', 'red', '#66FF00'])

# Use geocat.viz.util convenience function to set axes tick values
gv.set_axes_limits_and_ticks(ax, ylim=(-6.0, 8.5), yticks=[-3.0, 0.0, 3.0, 6.0])

# Set y_axis format
ax.yaxis.set_major_formatter(FormatStrFormatter('%.1f'))

# Use geocat.viz.util convenience function to add minor and major tick lines
gv.add_major_minor_ticks(ax, y_minor_per_major=3, x_minor_per_major=1, labelsize=16)

# Use geocat.viz.util convenience function to set spines visibility
gv.set_tick_direction_spine_visibility(
    ax, tick_direction='in', top_spine_visible=False, right_spine_visible=False
)

# Use geocat.viz.util convenience function to add title to the plot axis.
gv.set_titles_and_labels(ax, maintitle='Tailored Box Plot', maintitlefontsize=22)

# Set padding between ticks and tick labels
ax.tick_params(pad=9)

# Display Plot
plt.tight_layout()
plt.show()