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<span id="Test-Plotting-Functions"></span><div class="header">
<p>
Previous: <a href="Interacting-with-Plots.html" accesskey="p" rel="prev">Interacting with Plots</a>, Up: <a href="High_002dLevel-Plotting.html" accesskey="u" rel="up">High-Level Plotting</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Test-Plotting-Functions-1"></span><h4 class="subsection">15.2.11 Test Plotting Functions</h4>
<p>The functions <code>sombrero</code> and <code>peaks</code> provide a way to check
that plotting is working. Typing either <code>sombrero</code> or <code>peaks</code>
at the Octave prompt should display a three-dimensional plot.
</p>
<span id="XREFsombrero"></span><dl>
<dt id="index-sombrero">: <em></em> <strong>sombrero</strong> <em>()</em></dt>
<dt id="index-sombrero-1">: <em></em> <strong>sombrero</strong> <em>(<var>n</var>)</em></dt>
<dt id="index-sombrero-2">: <em><var>z</var> =</em> <strong>sombrero</strong> <em>(…)</em></dt>
<dt id="index-sombrero-3">: <em>[<var>x</var>, <var>y</var>, <var>z</var>] =</em> <strong>sombrero</strong> <em>(…)</em></dt>
<dd><p>Plot the familiar 3-D sombrero function.
</p>
<p>The function plotted is
</p>
<div class="example">
<pre class="example">z = sin (sqrt (x^2 + y^2)) / (sqrt (x^2 + y^2))
</pre></div>
<p>Called without a return argument, <code>sombrero</code> plots the surface of the
above function over the meshgrid [-8,8] using <code>surf</code>.
</p>
<p>If <var>n</var> is a scalar the plot is made with <var>n</var> grid lines.
The default value for <var>n</var> is 41.
</p>
<p>When called with output arguments, return the data for the function
evaluated over the meshgrid. This can subsequently be plotted with
<code>surf (<var>x</var>, <var>y</var>, <var>z</var>)</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFpeaks">peaks</a>, <a href="Three_002dDimensional-Plots.html#XREFmeshgrid">meshgrid</a>, <a href="Three_002dDimensional-Plots.html#XREFmesh">mesh</a>, <a href="Three_002dDimensional-Plots.html#XREFsurf">surf</a>.
</p></dd></dl>
<span id="XREFpeaks"></span><dl>
<dt id="index-peaks">: <em></em> <strong>peaks</strong> <em>()</em></dt>
<dt id="index-peaks-1">: <em></em> <strong>peaks</strong> <em>(<var>n</var>)</em></dt>
<dt id="index-peaks-2">: <em></em> <strong>peaks</strong> <em>(<var>x</var>, <var>y</var>)</em></dt>
<dt id="index-peaks-3">: <em><var>z</var> =</em> <strong>peaks</strong> <em>(…)</em></dt>
<dt id="index-peaks-4">: <em>[<var>x</var>, <var>y</var>, <var>z</var>] =</em> <strong>peaks</strong> <em>(…)</em></dt>
<dd><p>Plot a function with lots of local maxima and minima.
</p>
<p>The function has the form
</p>
<pre class="verbatim">f(x,y) = 3*(1-x)^2*exp(-x^2 - (y+1)^2) ...
- 10*(x/5 - x^3 - y^5)*exp(-x^2-y^2) ...
- 1/3*exp(-(x+1)^2 - y^2)
</pre>
<p>Called without a return argument, <code>peaks</code> plots the surface of the
above function using <code>surf</code>.
</p>
<p>If <var>n</var> is a scalar, <code>peaks</code> plots the value of the above
function on an <var>n</var>-by-<var>n</var> mesh over the range [-3,3]. The
default value for <var>n</var> is 49.
</p>
<p>If <var>n</var> is a vector, then it represents the grid values over which
to calculate the function. If <var>x</var> and <var>y</var> are specified then
the function value is calculated over the specified grid of vertices.
</p>
<p>When called with output arguments, return the data for the function
evaluated over the meshgrid. This can subsequently be plotted with
<code>surf (<var>x</var>, <var>y</var>, <var>z</var>)</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFsombrero">sombrero</a>, <a href="Three_002dDimensional-Plots.html#XREFmeshgrid">meshgrid</a>, <a href="Three_002dDimensional-Plots.html#XREFmesh">mesh</a>, <a href="Three_002dDimensional-Plots.html#XREFsurf">surf</a>.
</p></dd></dl>
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