.. _pylab_examples-multicolored_line: pylab_examples example code: multicolored_line.py ================================================= .. plot:: /home/tcaswell/other_source/matplotlib/doc/mpl_examples/pylab_examples/multicolored_line.py :: #!/usr/bin/env python ''' Color parts of a line based on its properties, e.g., slope. ''' import numpy as np import matplotlib.pyplot as plt from matplotlib.collections import LineCollection from matplotlib.colors import ListedColormap, BoundaryNorm x = np.linspace(0, 3 * np.pi, 500) y = np.sin(x) z = np.cos(0.5 * (x[:-1] + x[1:])) # first derivative # Create a colormap for red, green and blue and a norm to color # f' < -0.5 red, f' > 0.5 blue, and the rest green cmap = ListedColormap(['r', 'g', 'b']) norm = BoundaryNorm([-1, -0.5, 0.5, 1], cmap.N) # Create a set of line segments so that we can color them individually # This creates the points as a N x 1 x 2 array so that we can stack points # together easily to get the segments. The segments array for line collection # needs to be numlines x points per line x 2 (x and y) points = np.array([x, y]).T.reshape(-1, 1, 2) segments = np.concatenate([points[:-1], points[1:]], axis=1) # Create the line collection object, setting the colormapping parameters. # Have to set the actual values used for colormapping separately. lc = LineCollection(segments, cmap=cmap, norm=norm) lc.set_array(z) lc.set_linewidth(3) fig1 = plt.figure() plt.gca().add_collection(lc) plt.xlim(x.min(), x.max()) plt.ylim(-1.1, 1.1) # Now do a second plot coloring the curve using a continuous colormap t = np.linspace(0, 10, 200) x = np.cos(np.pi * t) y = np.sin(t) points = np.array([x, y]).T.reshape(-1, 1, 2) segments = np.concatenate([points[:-1], points[1:]], axis=1) lc = LineCollection(segments, cmap=plt.get_cmap('copper'), norm=plt.Normalize(0, 10)) lc.set_array(t) lc.set_linewidth(3) fig2 = plt.figure() plt.gca().add_collection(lc) plt.xlim(-1, 1) plt.ylim(-1, 1) plt.show() Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)