You are reading documentation for the unreleased version of Matplotlib. Try searching for the released version of this page instead?
Applications are open for the 2018 John Hunter Matplotlib Summer Fellowship. Apply now!
Version 2.2.2.post1768+g23420a4c1
matplotlib
Fork me on GitHub

Table Of Contents

Related Topics

Line Collection

Plotting lines with Matplotlib.

LineCollection allows one to plot multiple lines on a figure. Below we show off some of its properties.

import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
from matplotlib import colors as mcolors

import numpy as np

# In order to efficiently plot many lines in a single set of axes,
# Matplotlib has the ability to add the lines all at once. Here is a
# simple example showing how it is done.

x = np.arange(100)
# Here are many sets of y to plot vs x
ys = x[:50, np.newaxis] + x[np.newaxis, :]

segs = np.zeros((50, 100, 2))
segs[:, :, 1] = ys
segs[:, :, 0] = x

# Mask some values to test masked array support:
segs = np.ma.masked_where((segs > 50) & (segs < 60), segs)

# We need to set the plot limits.
fig, ax = plt.subplots()
ax.set_xlim(x.min(), x.max())
ax.set_ylim(ys.min(), ys.max())

# colors is sequence of rgba tuples
# linestyle is a string or dash tuple. Legal string values are
#          solid|dashed|dashdot|dotted.  The dash tuple is (offset, onoffseq)
#          where onoffseq is an even length tuple of on and off ink in points.
#          If linestyle is omitted, 'solid' is used
# See :class:`matplotlib.collections.LineCollection` for more information
colors = [mcolors.to_rgba(c)
          for c in plt.rcParams['axes.prop_cycle'].by_key()['color']]

line_segments = LineCollection(segs, linewidths=(0.5, 1, 1.5, 2),
                               colors=colors, linestyle='solid')
ax.add_collection(line_segments)
ax.set_title('Line collection with masked arrays')
plt.show()
../../_images/sphx_glr_line_collection_001.png

In order to efficiently plot many lines in a single set of axes, Matplotlib has the ability to add the lines all at once. Here is a simple example showing how it is done.

N = 50
x = np.arange(N)
# Here are many sets of y to plot vs x
ys = [x + i for i in x]

# We need to set the plot limits, they will not autoscale
fig, ax = plt.subplots()
ax.set_xlim(np.min(x), np.max(x))
ax.set_ylim(np.min(ys), np.max(ys))

# colors is sequence of rgba tuples
# linestyle is a string or dash tuple. Legal string values are
#          solid|dashed|dashdot|dotted.  The dash tuple is (offset, onoffseq)
#          where onoffseq is an even length tuple of on and off ink in points.
#          If linestyle is omitted, 'solid' is used
# See :class:`matplotlib.collections.LineCollection` for more information

# Make a sequence of x,y pairs
line_segments = LineCollection([np.column_stack([x, y]) for y in ys],
                               linewidths=(0.5, 1, 1.5, 2),
                               linestyles='solid')
line_segments.set_array(x)
ax.add_collection(line_segments)
axcb = fig.colorbar(line_segments)
axcb.set_label('Line Number')
ax.set_title('Line Collection with mapped colors')
plt.sci(line_segments)  # This allows interactive changing of the colormap.
plt.show()
../../_images/sphx_glr_line_collection_002.png