<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>pylab_examples example code: multicolored_line.py — Matplotlib 1.2.0 documentation</title> <link rel="stylesheet" href="../../_static/mpl.css" type="text/css" /> <link rel="stylesheet" href="../../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../../', VERSION: '1.2.0', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../../_static/jquery.js"></script> <script type="text/javascript" src="../../_static/underscore.js"></script> <script type="text/javascript" src="../../_static/doctools.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Matplotlib 1.2.0 documentation" href="../../_static/opensearch.xml"/> <link rel="top" title="Matplotlib 1.2.0 documentation" href="../../index.html" /> </head> <body> <!-- Piwik --> <script type="text/javascript"> if ("matplotlib.sourceforge.net" == document.location.hostname || "matplotlib.sf.net" == document.location.hostname) { var pkBaseURL = (("https:" == document.location.protocol) ? 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<h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li><a href="../../index.html">home</a>| </li> <li><a href="../../search.html">search</a>| </li> <li><a href="../index.html">examples</a>| </li> <li><a href="../../gallery.html">gallery</a>| </li> <li><a href="../../contents.html">docs</a> »</li> </ul> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../../_sources/examples/pylab_examples/multicolored_line.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input 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class="sd">'''</span> <span class="kn">import</span> <span class="nn">numpy</span> <span class="kn">as</span> <span class="nn">np</span> <span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span> <span class="kn">from</span> <span class="nn">matplotlib.collections</span> <span class="kn">import</span> <span class="n">LineCollection</span> <span class="kn">from</span> <span class="nn">matplotlib.colors</span> <span class="kn">import</span> <span class="n">ListedColormap</span><span class="p">,</span> <span class="n">BoundaryNorm</span> <span class="n">x</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">linspace</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">3</span> <span class="o">*</span> <span class="n">np</span><span class="o">.</span><span class="n">pi</span><span class="p">,</span> <span class="mi">500</span><span class="p">)</span> <span class="n">y</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">sin</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="n">z</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">cos</span><span class="p">(</span><span class="mf">0.5</span> <span class="o">*</span> <span class="p">(</span><span class="n">x</span><span class="p">[:</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="o">+</span> <span class="n">x</span><span class="p">[</span><span class="mi">1</span><span class="p">:]))</span> <span class="c"># first derivative</span> <span class="c"># Create a colormap for red, green and blue and a norm to color</span> <span class="c"># f' < -0.5 red, f' > 0.5 blue, and the rest green</span> <span class="n">cmap</span> <span class="o">=</span> <span class="n">ListedColormap</span><span class="p">([</span><span class="s">'r'</span><span class="p">,</span> <span class="s">'g'</span><span class="p">,</span> <span class="s">'b'</span><span class="p">])</span> <span class="n">norm</span> <span class="o">=</span> <span class="n">BoundaryNorm</span><span class="p">([</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="o">-</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">,</span> <span class="mi">1</span><span class="p">],</span> <span class="n">cmap</span><span class="o">.</span><span class="n">N</span><span class="p">)</span> <span class="c"># Create a set of line segments so that we can color them individually</span> <span class="c"># This creates the points as a N x 1 x 2 array so that we can stack points</span> <span class="c"># together easily to get the segments. The segments array for line collection</span> <span class="c"># needs to be numlines x points per line x 2 (x and y)</span> <span class="n">points</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">([</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">])</span><span class="o">.</span><span class="n">T</span><span class="o">.</span><span class="n">reshape</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span> <span class="n">segments</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">concatenate</span><span class="p">([</span><span class="n">points</span><span class="p">[:</span><span class="o">-</span><span class="mi">1</span><span class="p">],</span> <span class="n">points</span><span class="p">[</span><span class="mi">1</span><span class="p">:]],</span> <span class="n">axis</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="c"># Create the line collection object, setting the colormapping parameters.</span> <span class="c"># Have to set the actual values used for colormapping separately.</span> <span class="n">lc</span> <span class="o">=</span> <span class="n">LineCollection</span><span class="p">(</span><span class="n">segments</span><span class="p">,</span> <span class="n">cmap</span><span class="o">=</span><span class="n">cmap</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">norm</span><span class="p">)</span> <span class="n">lc</span><span class="o">.</span><span class="n">set_array</span><span class="p">(</span><span class="n">z</span><span class="p">)</span> <span class="n">lc</span><span class="o">.</span><span class="n">set_linewidth</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span> <span class="n">fig1</span> <span class="o">=</span> <span class="n">plt</span><span class="o">.</span><span class="n">figure</span><span class="p">()</span> <span class="n">plt</span><span class="o">.</span><span class="n">gca</span><span class="p">()</span><span class="o">.</span><span class="n">add_collection</span><span class="p">(</span><span class="n">lc</span><span class="p">)</span> <span class="n">plt</span><span class="o">.</span><span class="n">xlim</span><span class="p">(</span><span class="n">x</span><span class="o">.</span><span class="n">min</span><span class="p">(),</span> <span class="n">x</span><span class="o">.</span><span class="n">max</span><span class="p">())</span> <span class="n">plt</span><span class="o">.</span><span class="n">ylim</span><span class="p">(</span><span class="o">-</span><span class="mf">1.1</span><span class="p">,</span> <span class="mf">1.1</span><span class="p">)</span> <span class="c"># Now do a second plot coloring the curve using a continuous colormap</span> <span class="n">t</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">linspace</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">200</span><span class="p">)</span> <span class="n">x</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">cos</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">pi</span> <span class="o">*</span> <span class="n">t</span><span class="p">)</span> <span class="n">y</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">sin</span><span class="p">(</span><span class="n">t</span><span class="p">)</span> <span class="n">points</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">([</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">])</span><span class="o">.</span><span class="n">T</span><span class="o">.</span><span class="n">reshape</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span> <span class="n">segments</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">concatenate</span><span class="p">([</span><span class="n">points</span><span class="p">[:</span><span class="o">-</span><span class="mi">1</span><span class="p">],</span> <span class="n">points</span><span class="p">[</span><span class="mi">1</span><span class="p">:]],</span> <span class="n">axis</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="n">lc</span> <span class="o">=</span> <span class="n">LineCollection</span><span class="p">(</span><span class="n">segments</span><span class="p">,</span> <span class="n">cmap</span><span class="o">=</span><span class="n">plt</span><span class="o">.</span><span class="n">get_cmap</span><span class="p">(</span><span class="s">'copper'</span><span class="p">),</span> <span class="n">norm</span><span class="o">=</span><span class="n">plt</span><span class="o">.</span><span class="n">Normalize</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">10</span><span class="p">))</span> <span class="n">lc</span><span class="o">.</span><span class="n">set_array</span><span class="p">(</span><span class="n">t</span><span class="p">)</span> <span class="n">lc</span><span class="o">.</span><span class="n">set_linewidth</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span> <span class="n">fig2</span> <span class="o">=</span> <span class="n">plt</span><span class="o">.</span><span class="n">figure</span><span class="p">()</span> <span class="n">plt</span><span class="o">.</span><span class="n">gca</span><span class="p">()</span><span class="o">.</span><span class="n">add_collection</span><span class="p">(</span><span class="n">lc</span><span class="p">)</span> <span class="n">plt</span><span class="o">.</span><span class="n">xlim</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="n">plt</span><span class="o">.</span><span class="n">ylim</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span> </pre></div> </div> <p>Keywords: python, matplotlib, pylab, example, codex (see <a 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