@unutbu’s answer is the right approach if you have a small number of lines. (And if you’re wanting to add a legend, you presumably do!)
Just to show the other option, though, you can still use a LineCollection, you just need to use “proxy artists” for the legend:
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
from matplotlib.lines import Line2D
# The line format you curently have:
lines = [[(0, 1, 2, 3, 4), (4, 5, 6, 7, 8)],
[(0, 1, 2, 3, 4), (0, 1, 2, 3, 4)],
[(0, 1, 2, 3, 4), (8, 7, 6, 5, 4)],
[(4, 5, 6, 7, 8), (0, 1, 2, 3, 4)]]
# Reformat it to what `LineCollection` expects:
lines = [tuple(zip(x, y)) for x, y in lines]
z = np.array([0.1, 9.4, 3.8, 2.0])
fig, ax = plt.subplots()
lines = LineCollection(lines, array=z, linewidths=5,
cmap=plt.cm.rainbow, norm=plt.Normalize(z.min(), z.max()))
ax.add_collection(lines)
fig.colorbar(lines)
# Manually adding artists doesn't rescale the plot, so we need to autoscale
ax.autoscale()
def make_proxy(zvalue, scalar_mappable, **kwargs):
color = scalar_mappable.cmap(scalar_mappable.norm(zvalue))
return Line2D([0, 1], [0, 1], color=color, **kwargs)
proxies = [make_proxy(item, lines, linewidth=5) for item in z]
ax.legend(proxies, ['Line 1', 'Line 2', 'Line 3', 'Line 4'])
plt.show()
