NCL_xy_35.py

This script illustrates the following concepts:

• Use of opacity resources to control opacity of curves and markers in XYPlots.

• How to set line opacity and marker opacity to different values using RGBA tuples

• Opacity is still functional in colorless plots

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

• Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/xy_35.ncl

• Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/xy_35_lg.png

Import packages:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import colors

import geocat.viz as gv

Create data:

# Make array of x-values, 64 evenly spaced values between 0 and 1
f = np.linspace(0., 1., 64)

twopi = 2 * np.pi

# Create three arrays of y-values to be plotted
x = np.cos(f * 2 * twopi)
y = np.cos(f * 3 * twopi)
z = x * y

Plot:

# Create figure with 6 axes
fig, axes = plt.subplots(figsize=(7, 10), nrows=3, ncols=2)
plt.subplots_adjust(wspace=0.3, hspace=.4)

# Plot first graph
axesList = [
    axes[0, 0], axes[0, 1], axes[1, 0], axes[1, 1], axes[2, 0], axes[2, 1]
]

# Create array of titles of each plot
titles = [
    'Opaque lines', 'Uniformly translucent', 'Independently translucent',
    'Uniformly translucent markers', 'Independently translucent markers',
    'Opacities still apply in MonoColor modes'
]

# Create ticks, axis limits, and titles for each of the 6 plots
for ax in range(6):

    # Use geocat-viz function to set main title of plot
    gv.set_titles_and_labels(axesList[ax],
                             maintitle=titles[ax],
                             maintitlefontsize=10)

    # Use geocat-viz function to set limits and tick locations on x and y axes
    gv.set_axes_limits_and_ticks(axesList[ax],
                                 xlim=[0, 1],
                                 ylim=[-1.2, 1.2],
                                 yticks=np.arange(-1.5, 1.5, 0.5),
                                 yticklabels=np.arange(-1.5, 1.5, 0.5))

    # Use geocat-viz function to add major and minor ticks on the x and y axes
    gv.add_major_minor_ticks(axesList[ax],
                             x_minor_per_major=4,
                             y_minor_per_major=5,
                             labelsize="small")

# Set standard alpha (transparency) value
alpha = 0.4

# Plot first graph:

# Plot x, y, and z lines
line1 = axesList[0].plot(f, x, color='red')
line2 = axesList[0].plot(f, y, color='limegreen')
line3 = axesList[0].plot(f, z, color='blue')

# Plot second graph:

# Plot x, y, and z lines with the same level of transparency
line1 = axesList[1].plot(f, x, color='red', alpha=alpha)
line2 = axesList[1].plot(f, y, color='limegreen', alpha=alpha)
line3 = axesList[1].plot(f, z, color='blue', alpha=alpha)

# Plot third graph:

# Plot x, y, and z lines with varying transparencies
line1 = axesList[2].plot(f, x, color='red', alpha=0.8)
line2 = axesList[2].plot(f, y, color='limegreen', alpha=0.4)
line3 = axesList[2].plot(f, z, color='blue', alpha=0.15)

# Plot fourth graph:

# Plot x, y, and z lines and markers with same level of transparency
# 'ms' is the marker size
# 'markevery' allows you to place a marker every num steps in the x direction
# 'mec' is marker edge color
# 'mfc' is marker face color
line1 = axesList[3].plot(f,
                         x,
                         'o',
                         ls='-',
                         color='red',
                         alpha=alpha,
                         ms=3,
                         markevery=.05,
                         mec='None',
                         mfc='limegreen')
line2 = axesList[3].plot(f,
                         y,
                         'o',
                         ls='-',
                         color='limegreen',
                         alpha=alpha,
                         ms=3,
                         markevery=.05,
                         mec='None',
                         mfc='blue')
line3 = axesList[3].plot(f,
                         z,
                         'o',
                         ls='-',
                         color='blue',
                         alpha=alpha,
                         ms=3,
                         markevery=.05,
                         mec='None',
                         mfc='red')

# Plot fifth graph:

# Create RGBA tuples for lines
lcolor1 = colors.to_rgba('red', alpha=alpha)
lcolor2 = colors.to_rgba('limegreen', alpha=alpha)
lcolor3 = colors.to_rgba('blue', alpha=alpha)

# Create RGBA tuples for markers
mcolor1 = colors.to_rgba('limegreen', alpha=1.0)
mcolor2 = colors.to_rgba('blue', alpha=0.4)
mcolor3 = colors.to_rgba('red', alpha=0.15)

# Plot x, y, and z lines and markers- the lines have the same
# transparency level, but the markers vary in alpha value
line1 = axesList[4].plot(f,
                         x,
                         'o',
                         ls='-',
                         color=lcolor1,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor1)
line2 = axesList[4].plot(f,
                         y,
                         'o',
                         ls='-',
                         color=lcolor2,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor2)
line3 = axesList[4].plot(f,
                         z,
                         'o',
                         ls='-',
                         color=lcolor3,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor3)

# Plot sixth graph:

# Create RGBA tuples for lines
lcolor1 = colors.to_rgba('black', alpha=alpha)
lcolor2 = colors.to_rgba('black', alpha=alpha)
lcolor3 = colors.to_rgba('black', alpha=alpha)

# Create RGBA tuples for markers
mcolor1 = colors.to_rgba('black', alpha=1.0)
mcolor2 = colors.to_rgba('black', alpha=0.4)
mcolor3 = colors.to_rgba('black', alpha=0.15)

# Plot x, y, and z lines and markers in black- the lines have the same
# transparency level, but the markers vary in alpha value
line1 = axesList[5].plot(f,
                         x,
                         'o',
                         ls='-',
                         color=lcolor1,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor1)
line2 = axesList[5].plot(f,
                         y,
                         'o',
                         ls='-',
                         color=lcolor2,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor2)
line3 = axesList[5].plot(f,
                         z,
                         'o',
                         ls='-',
                         color=lcolor3,
                         ms=3,
                         markevery=.1,
                         mec='None',
                         mfc=mcolor3)

plt.show()