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<html>
<head>
<title>
FEM2D_SCALAR_DISPLAY_GPL - Surface Plot of FEM2D Data Using GNUPLOT
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
FEM2D_SCALAR_DISPLAY_GPL <br> Surface Plot of FEM2D Data Using GNUPLOT
</h1>
<hr>
<p>
<b>FEM2D_SCALAR_DISPLAY_GPL</b>
is a MATLAB program which
reads datafiles describing a set of nodes, their triangulation, and the
value of a scalar quantity at each node, and creates a graphics file
of the corresponding surface plot, which can be displayed by GNUPLOT.
</p>
<p>
The program reads three data files:
<ul>
<li>
<i>prefix</i>_nodes.txt, a node file, containing
X, Y coordinates of points;
</li>
<li>
<i>prefix</i>_elements.txt, an element file,
containing a list of sets of three points making up each
triangular element; (if this file does not exist, the
program will generate the element data automatically).
</li>
<li>
<i>prefix</i>_values.txt, a values file,
containing the values of a scalar function U(X,Y) evaluated
at each node.
</li>
</ul>
</p>
<h3 align = "center">
Usage:
</h3>
<p>
<blockquote>
<b>fem2d_scalar_display_gpl</b> ( <i>'prefix'</i> )
</blockquote>
where <i>'prefix'</i> is the common prefix for the node, element and value files:
</p>
<p>
The program creates two files:
<ul>
<li>
<i>prefix</i>_data.txt, containing data;
</li>
<li>
<i>prefix</i>_commands.txt, containing commands for GNUPLOT.
</li>
</ul>
</p>
<p>
To actually create the plot, type
<blockquote>
gnuplot < <i>prefix</i>_commands.txt
</blockquote>
which will create the file <i>prefix</i>.png
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files described and made available on this web page
are distributed under
<a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
</p>
<h3 align = "center">
Languages:
</h3>
<p>
<b>FEM2D_SCALAR_DISPLAY_GPL</b> is available in
<a href = "../../m_src/fem2d_scalar_display_gpl/fem2d_scalar_display_gpl.html">a MATLAB version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../m_src/dist_plot/dist_plot.html">
DIST_PLOT</a>,
a MATLAB program which
makes contour plots of the distance function,
as defined and used in Persson and Strang's distmesh code;
</p>
<p>
<a href = "../../m_src/fem2d_mesh_display/fem2d_mesh_display.html">
FEM2D_MESH_DISPLAY</a>,
a MATLAB program which
reads the FEM model of a 2D mesh, consisting of polygonal elements of
any uniform order, and displays an image of the elements and nodes,
with optional numbering.
</p>
<p>
<a href = "../../m_src/fem2d_scalar_display/fem2d_scalar_display.html">
FEM2D_SCALAR_DISPLAY</a>,
a MATLAB program which
reads information about nodes, elements and nodal values for a
2D finite element method (FEM) and creates a surface plot of U(X,Y),
using the MATLAB graphics system.
</p>
<p>
<a href = "../../m_src/fem2d_scalar_display_brief/fem2d_scalar_display_brief.html">
FEM2D_SCALAR_DISPLAY_BRIEF</a>,
a MATLAB program which
reads information about nodes, elements and nodal values for a
2D finite element method (FEM) and creates a surface plot of U(X,Y),
using the MATLAB graphics system, in 5 lines of code.
</p>
<p>
<a href = "../../examples/fenics_to_fem/fenics_to_fem.html">
FENICS_TO_FEM</a>,
examples which
illustrate how a mesh or scalar function computed by the FENICS program
can be written to FEM files, which can then be used to create
images, or as input to meshing programs or other analysis tools.
</p>
<p>
<a href = "../../examples/gnuplot/gnuplot.html">
GNUPLOT</a>,
examples which
illustrate the use of the gnuplot graphics program.
</p>
<p>
<a href = "../../data/gpl/gpl.html">
GPL</a>,
a data directory which
contains examples of GPL files,
a graphics file format used by gnuplot;
</p>
<p>
<a href = "../../m_src/gpl_display/gpl_display.html">
GPL_DISPLAY</a>,
a MATLAB library which
tries to read the data in a typical gnuplot GPL file,
and display it in a more attractive way than gnuplot is capable of.
</p>
<p>
<a href = "../../m_src/triangulation_order3_contour/triangulation_order3_contour.html">
TRIANGULATION_ORDER3_CONTOUR</a>,
a MATLAB program which
can display a contour plot
of scalar data defined on a triangulation of order 3.
</p>
<p>
<a href = "../../m_src/twod_plotc/twod_plotc.html">
TWOD_PLOTC</a>,
a MATLAB program which
makes a color contour plot of scalar data defined on a 2D finite element mesh.
</p>
<h3 align = "center">
Source Code:
</h3>
<p>
<ul>
<li>
<a href = "fem2d_scalar_display_gpl.m">
fem2d_scalar_display_gpl.m</a>,
the routine for creating the surface plot;
</li>
</ul>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<b>ELL</b> is an L-shaped region on which the function U=X^2+Y^2
is defined.
<ul>
<li>
<a href = "ell_nodes.txt">ell_nodes.txt</a>,
a node file;
</li>
<li>
<a href = "ell_elements.txt">ell_elements.txt</a>,
an element file;
</li>
<li>
<a href = "ell_values.txt">ell_values.txt</a>,
a value file;
</li>
<li>
<a href = "ell_data.txt">ell_data.txt</a>,
the data file that is created by this program.
</li>
<li>
<a href = "ell_commands.txt">ell_commands.txt</a>,
the command file that is created by this program.
</li>
<li>
<a href = "ell.png">ell.png</a>,
a PNG image, created by GNUPLOT;
</li>
</ul>
</p>
<p>
<b>SPIKE</b> is a circular region on which a solution of the
Poisson equation forms an off-centered spike.
<ul>
<li>
<a href = "spike_nodes.txt">spike_nodes.txt</a>,
a node file;
</li>
<li>
<a href = "spike_elements.txt">spike_elements.txt</a>,
an element file;
</li>
<li>
<a href = "spike_values.txt">spike_values.txt</a>,
a value file;
</li>
<li>
<a href = "spike_data.txt">spike_data.txt</a>,
the data file that is created by this program.
</li>
<li>
<a href = "spike_commands.txt">spike_commands.txt</a>,
the command file that is created by this program.
</li>
<li>
<a href = "spike.png">spike.png</a>,
a PNG image, created by GNUPLOT;
</li>
</ul>
</p>
<p>
You can go up one level to <a href = "../m_src.html">
the MATLAB source codes</a>.
</p>
<hr>
<i>
Last revised on 02 November 2014.
</i>
<!-- John Burkardt -->
</body>
</html>