Plotting a Line in Varying Colors

Problem Statement

Given two lists, latt and lont, the goal is to plot a single line where each segment of 10 consecutive points is represented in a different color.

Solution

Limited Number of Line Segments

If the number of line segments is small, such as 10 or less, a simple approach is to use a loop to plot each segment with a unique color.

import numpy as np
import matplotlib.pyplot as plt

# Generate random colors
def uniqueish_color():
    return plt.cm.gist_ncar(np.random.random())

# Plot the line segments
xy = (np.random.random((10, 2)) - 0.5).cumsum(axis=0)
fig, ax = plt.subplots()
for start, stop in zip(xy[:-1], xy[1:]):
    x, y = zip(start, stop)
    ax.plot(x, y, color=uniqueish_color())
plt.show()

Large Number of Line Segments

For a large number of line segments, using a loop can be slow. Instead, create a LineCollection object.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection

# Generate the line segments
xy = (np.random.random((1000, 2)) - 0.5).cumsum(axis=0)
xy = xy.reshape(-1, 1, 2)
segments = np.hstack([xy[:-1], xy[1:]])

# Create a LineCollection object
fig, ax = plt.subplots()
coll = LineCollection(segments, cmap=plt.cm.gist_ncar)

# Set the color array
coll.set_array(np.random.random(xy.shape[0]))

# Add the LineCollection to the axes
ax.add_collection(coll)
ax.autoscale_view()

# Display the plot
plt.show()

Selecting Colors

For both approaches, we use the "gist_ncar" colormap to generate unique colors. Refer to this page for other colormap options: http://matplotlib.org/examples/color/colormaps_reference.html