<!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: custom_cmap.py — Matplotlib v1.1.1 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: '1.1.1',
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 v1.1.1 documentation"
href="../../_static/opensearch.xml"/>
<link rel="top" title="Matplotlib v1.1.1 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) ? "https://apps.sourceforge.net/piwik/matplotlib/" : "http://apps.sourceforge.net/piwik/matplotlib/");
document.write(unescape("%3Cscript src='" + pkBaseURL + "piwik.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>
<script type="text/javascript">
if ("matplotlib.sourceforge.net" == document.location.hostname ||
"matplotlib.sf.net" == document.location.hostname) {
piwik_action_name = '';
piwik_idsite = 1;
piwik_url = pkBaseURL + "piwik.php";
piwik_log(piwik_action_name, piwik_idsite, piwik_url);
document.write(unescape('%3Cobject%3E%3Cnoscript%3E%3Cp%3E%3Cimg src="http://apps.sourceforge.net/piwik/matplotlib/piwik.php?idsite=1" alt="piwik"/%3E%3C/p%3E%3C/noscript%3E%3C/object%3E'));
}
</script>
<!-- End Piwik Tag -->
<link rel="shortcut icon" href="_static/favicon.ico">
<div style="background-color: white; text-align: left; padding: 10px 10px 15px 15px">
<a href="../../index.html"><img src="../../_static/logo2.png" border="0" alt="matplotlib"/></a>
</div>
<div class="related">
<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/custom_cmap.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" size="18" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
<p class="searchtip" style="font-size: 90%">
Enter search terms or a module, class or function name.
</p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
</div>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body">
<div class="section" id="pylab-examples-example-code-custom-cmap-py">
<span id="pylab-examples-custom-cmap"></span><h1>pylab_examples example code: custom_cmap.py<a class="headerlink" href="#pylab-examples-example-code-custom-cmap-py" title="Permalink to this headline">ΒΆ</a></h1>
<p>(<a class="reference external" href="../../mpl_examples/pylab_examples/custom_cmap.py">Source code</a>, <a class="reference external" href="../../mpl_examples/pylab_examples/custom_cmap.png">png</a>, <a class="reference external" href="../../mpl_examples/pylab_examples/custom_cmap.hires.png">hires.png</a>, <a class="reference external" href="../../mpl_examples/pylab_examples/custom_cmap.pdf">pdf</a>)</p>
<div class="figure">
<img alt="../../_images/custom_cmap.png" src="../../_images/custom_cmap.png" />
</div>
<div class="highlight-python"><div class="highlight"><pre><span class="c">#!/usr/bin/env python</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.colors</span> <span class="kn">import</span> <span class="n">LinearSegmentedColormap</span>
<span class="sd">"""</span>
<span class="sd">Example: suppose you want red to increase from 0 to 1 over the bottom</span>
<span class="sd">half, green to do the same over the middle half, and blue over the top</span>
<span class="sd">half. Then you would use:</span>
<span class="sd">cdict = {'red': ((0.0, 0.0, 0.0),</span>
<span class="sd"> (0.5, 1.0, 1.0),</span>
<span class="sd"> (1.0, 1.0, 1.0)),</span>
<span class="sd"> 'green': ((0.0, 0.0, 0.0),</span>
<span class="sd"> (0.25, 0.0, 0.0),</span>
<span class="sd"> (0.75, 1.0, 1.0),</span>
<span class="sd"> (1.0, 1.0, 1.0)),</span>
<span class="sd"> 'blue': ((0.0, 0.0, 0.0),</span>
<span class="sd"> (0.5, 0.0, 0.0),</span>
<span class="sd"> (1.0, 1.0, 1.0))}</span>
<span class="sd">If, as in this example, there are no discontinuities in the r, g, and b</span>
<span class="sd">components, then it is quite simple: the second and third element of</span>
<span class="sd">each tuple, above, is the same--call it "y". The first element ("x")</span>
<span class="sd">defines interpolation intervals over the full range of 0 to 1, and it</span>
<span class="sd">must span that whole range. In other words, the values of x divide the</span>
<span class="sd">0-to-1 range into a set of segments, and y gives the end-point color</span>
<span class="sd">values for each segment.</span>
<span class="sd">Now consider the green. cdict['green'] is saying that for</span>
<span class="sd">0 <= x <= 0.25, y is zero; no green.</span>
<span class="sd">0.25 < x <= 0.75, y varies linearly from 0 to 1.</span>
<span class="sd">x > 0.75, y remains at 1, full green.</span>
<span class="sd">If there are discontinuities, then it is a little more complicated.</span>
<span class="sd">Label the 3 elements in each row in the cdict entry for a given color as</span>
<span class="sd">(x, y0, y1). Then for values of x between x[i] and x[i+1] the color</span>
<span class="sd">value is interpolated between y1[i] and y0[i+1].</span>
<span class="sd">Going back to the cookbook example, look at cdict['red']; because y0 !=</span>
<span class="sd">y1, it is saying that for x from 0 to 0.5, red increases from 0 to 1,</span>
<span class="sd">but then it jumps down, so that for x from 0.5 to 1, red increases from</span>
<span class="sd">0.7 to 1. Green ramps from 0 to 1 as x goes from 0 to 0.5, then jumps</span>
<span class="sd">back to 0, and ramps back to 1 as x goes from 0.5 to 1.</span>
<span class="sd">row i: x y0 y1</span>
<span class="sd"> /</span>
<span class="sd"> /</span>
<span class="sd">row i+1: x y0 y1</span>
<span class="sd">Above is an attempt to show that for x in the range x[i] to x[i+1], the</span>
<span class="sd">interpolation is between y1[i] and y0[i+1]. So, y0[0] and y1[-1] are</span>
<span class="sd">never used.</span>
<span class="sd">"""</span>
<span class="n">cdict1</span> <span class="o">=</span> <span class="p">{</span><span class="s">'red'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)),</span>
<span class="s">'green'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)),</span>
<span class="s">'blue'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">))</span>
<span class="p">}</span>
<span class="n">cdict2</span> <span class="o">=</span> <span class="p">{</span><span class="s">'red'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)),</span>
<span class="s">'green'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)),</span>
<span class="s">'blue'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.1</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">))</span>
<span class="p">}</span>
<span class="n">cdict3</span> <span class="o">=</span> <span class="p">{</span><span class="s">'red'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.25</span><span class="p">,</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.8</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.75</span><span class="p">,</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.4</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)),</span>
<span class="s">'green'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.25</span><span class="p">,</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">0.9</span><span class="p">,</span> <span class="mf">0.9</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.75</span><span class="p">,</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)),</span>
<span class="s">'blue'</span><span class="p">:</span> <span class="p">((</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.4</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.25</span><span class="p">,</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.5</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.8</span><span class="p">),</span>
<span class="p">(</span><span class="mf">0.75</span><span class="p">,</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">),</span>
<span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">))</span>
<span class="p">}</span>
<span class="c"># Now we will use this example to illustrate 3 ways of</span>
<span class="c"># handling custom colormaps.</span>
<span class="c"># First, the most direct and explicit:</span>
<span class="n">blue_red1</span> <span class="o">=</span> <span class="n">LinearSegmentedColormap</span><span class="p">(</span><span class="s">'BlueRed1'</span><span class="p">,</span> <span class="n">cdict1</span><span class="p">)</span>
<span class="c"># Second, create the map explicitly and register it.</span>
<span class="c"># Like the first method, this method works with any kind</span>
<span class="c"># of Colormap, not just</span>
<span class="c"># a LinearSegmentedColormap:</span>
<span class="n">blue_red2</span> <span class="o">=</span> <span class="n">LinearSegmentedColormap</span><span class="p">(</span><span class="s">'BlueRed2'</span><span class="p">,</span> <span class="n">cdict2</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">register_cmap</span><span class="p">(</span><span class="n">cmap</span><span class="o">=</span><span class="n">blue_red2</span><span class="p">)</span>
<span class="c"># Third, for LinearSegmentedColormap only,</span>
<span class="c"># leave everything to register_cmap:</span>
<span class="n">plt</span><span class="o">.</span><span class="n">register_cmap</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'BlueRed3'</span><span class="p">,</span> <span class="n">data</span><span class="o">=</span><span class="n">cdict3</span><span class="p">)</span> <span class="c"># optional lut kwarg</span>
<span class="n">x</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">arange</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">np</span><span class="o">.</span><span class="n">pi</span><span class="p">,</span> <span class="mf">0.1</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">arange</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</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="mf">0.1</span><span class="p">)</span>
<span class="n">X</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">meshgrid</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="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="n">X</span><span class="p">)</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">Y</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span><span class="mi">4</span><span class="p">))</span>
<span class="n">plt</span><span class="o">.</span><span class="n">subplots_adjust</span><span class="p">(</span><span class="n">wspace</span><span class="o">=</span><span class="mf">0.3</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">subplot</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</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">imshow</span><span class="p">(</span><span class="n">Z</span><span class="p">,</span> <span class="n">interpolation</span><span class="o">=</span><span class="s">'nearest'</span><span class="p">,</span> <span class="n">cmap</span><span class="o">=</span><span class="n">blue_red1</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">colorbar</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">subplot</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</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">'BlueRed2'</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">imshow</span><span class="p">(</span><span class="n">Z</span><span class="p">,</span> <span class="n">interpolation</span><span class="o">=</span><span class="s">'nearest'</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">plt</span><span class="o">.</span><span class="n">colorbar</span><span class="p">()</span>
<span class="c"># Now we will set the third cmap as the default. One would</span>
<span class="c"># not normally do this in the middle of a script like this;</span>
<span class="c"># it is done here just to illustrate the method.</span>
<span class="n">plt</span><span class="o">.</span><span class="n">rcParams</span><span class="p">[</span><span class="s">'image.cmap'</span><span class="p">]</span> <span class="o">=</span> <span class="s">'BlueRed3'</span>
<span class="c"># Also see below for an alternative, particularly for</span>
<span class="c"># interactive use.</span>
<span class="n">plt</span><span class="o">.</span><span class="n">subplot</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">imshow</span><span class="p">(</span><span class="n">Z</span><span class="p">,</span> <span class="n">interpolation</span><span class="o">=</span><span class="s">'nearest'</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">colorbar</span><span class="p">()</span>
<span class="c"># Or as yet another variation, we could replace the rcParams</span>
<span class="c"># specification *before* the imshow with the following *after*</span>
<span class="c"># imshow:</span>
<span class="c">#</span>
<span class="c"># plt.set_cmap('BlueRed3')</span>
<span class="c">#</span>
<span class="c"># This sets the new default *and* sets the colormap of the last</span>
<span class="c"># image-like item plotted via pyplot, if any.</span>
<span class="n">plt</span><span class="o">.</span><span class="n">suptitle</span><span class="p">(</span><span class="s">'Custom Blue-Red colormaps'</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 class="reference internal" href="../../faq/howto_faq.html#how-to-search-examples"><em>Search examples</em></a>)</p>
</div>
</div>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../../genindex.html" title="General Index"
>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="footer">
© Copyright 2008, John Hunter, Darren Dale, Michael Droettboom.
Last updated on Oct 04, 2012.
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.0.7.
</div>
</body>
</html>
distrib
>
Mandriva
>
2010.2
>
i586
>
media
>
contrib-backports
>
by-pkgid
>
a44f8c7e78ee9c5838c1fb080c9e7630
>
files
>
2096
