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<html>
<head>
<title>
PWL_INTERP_1D - Piecewise Linear Interpolation in 1D
</title>
</head>
<body bgcolor="#eeeeee" link="#cc0000" alink="#ff3300" vlink="#000055">
<h1 align = "center">
PWL_INTERP_1D <br> Piecewise Linear Interpolation in 1D
</h1>
<hr>
<p>
<b>PWL_INTERP_1D</b>
is a MATLAB library which
interpolates a set of data with a piecewise linear function.
</p>
<p>
<b>PWL_INTERP_1D</b> needs the R8LIB library. The test code
also needs the TEST_INTERP library.
</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>PWL_INTERP_1D</b> is available in
<a href = "../../c_src/pwl_interp_1d/pwl_interp_1d.html">a C version</a> and
<a href = "../../cpp_src/pwl_interp_1d/pwl_interp_1d.html">a C++ version</a> and
<a href = "../../f77_src/pwl_interp_1d/pwl_interp_1d.html">a FORTRAN77 version</a> and
<a href = "../../f_src/pwl_interp_1d/pwl_interp_1d.html">a FORTRAN90 version</a> and
<a href = "../../m_src/pwl_interp_1d/pwl_interp_1d.html">a MATLAB version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../m_src/barycentric_interp_1d/barycentric_interp_1d.html">
BARYCENTRIC_INTERP_1D</a>,
a MATLAB library which
defines and evaluates the barycentric Lagrange polynomial p(x)
which interpolates a set of data, so that p(x(i)) = y(i).
The barycentric approach means that very high degree polynomials can
safely be used.
</p>
<p>
<a href = "../../m_src/chebyshev_interp_1d/chebyshev_interp_1d.html">
CHEBYSHEV_INTERP_1D</a>,
a MATLAB library which
determines the combination of Chebyshev polynomials which
interpolates a set of data, so that p(x(i)) = y(i).
</p>
<p>
<a href = "../../m_src/lagrange_interp_1d/lagrange_interp_1d.html">
LAGRANGE_INTERP_1D</a>,
a MATLAB library which
defines and evaluates the Lagrange polynomial p(x)
which interpolates a set of data, so that p(x(i)) = y(i).
</p>
<p>
<a href = "../../m_src/nearest_interp_1d/nearest_interp_1d.html">
NEAREST_INTERP_1D</a>,
a MATLAB library which
interpolates a set of data using a piecewise constant interpolant
defined by the nearest neighbor criterion.
</p>
<p>
<a href = "../../m_src/pwl_interp_2d/pwl_interp_2d.html">
PWL_INTERP_2D</a>,
a MATLAB library which
evaluates a piecewise linear interpolant to data defined on
a regular 2D grid.
</p>
<p>
<a href = "../../m_src/r8lib/r8lib.html">
R8LIB</a>,
a MATLAB library which
contains many utility routines using double precision real (R8) arithmetic.
</p>
<p>
<a href = "../../m_src/rbf_interp_1d/rbf_interp_1d.html">
RBF_INTERP_1D</a>,
a MATLAB library which
defines and evaluates radial basis function (RBF) interpolants to 1D data.
</p>
<p>
<a href = "../../m_src/pwl_approx_1d/pwl_approx_1d.html">
PWL_APPROX_1D</a>,
a MATLAB library which
approximates a set of data using a piecewise linear function.
</p>
<p>
<a href = "../../m_src/shepard_interp_1d/shepard_interp_1d.html">
SHEPARD_INTERP_1D</a>,
a MATLAB library which
defines and evaluates Shepard interpolants to 1D data,
which are based on inverse distance weighting.
</p>
<p>
<a href = "../../m_src/test_interp/test_interp.html">
TEST_INTERP</a>,
a MATLAB library which
defines a number of test problems for interpolation,
provided as a set of (x,y) data.
</p>
<p>
<a href = "../../m_src/test_interp_1d/test_interp_1d.html">
TEST_INTERP_1D</a>,
a MATLAB library which
defines test problems for interpolation of data y(x),
depending on a 2D argument.
</p>
<p>
<a href = "../../m_src/vandermonde_interp_1d/vandermonde_interp_1d.html">
VANDERMONDE_INTERP_1D</a>,
a MATLAB library which
finds a polynomial interpolant to a function of 1D data
by setting up and solving a linear system for the polynomial coefficients,
involving the Vandermonde matrix.
</p>
<h3 align = "center">
Reference:
</h3>
<p>
<ol>
<li>
Kendall Atkinson,<br>
An Introduction to Numerical Analysis,<br>
Prentice Hall, 1989,<br>
ISBN: 0471624896,<br>
LC: QA297.A94.1989.
</li>
<li>
Philip Davis,<br>
Interpolation and Approximation,<br>
Dover, 1975,<br>
ISBN: 0-486-62495-1,<br>
LC: QA221.D33
</li>
<li>
David Kahaner, Cleve Moler, Steven Nash,<br>
Numerical Methods and Software,<br>
Prentice Hall, 1989,<br>
ISBN: 0-13-627258-4,<br>
LC: TA345.K34.
</li>
</ol>
</p>
<h3 align = "center">
Source Code:
</h3>
<p>
<ul>
<li>
<a href = "pwl_basis_1d.m">pwl_basis_1d.m</a>,
evaluates a piecewise linear interpolant basis function.
</li>
<li>
<a href = "pwl_interp_1d.m">pwl_interp_1d.m</a>,
evaluates a piecewise linear interpolant.
</li>
</ul>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
The test code requires the <b>test_interp</b> library as well.
<ul>
<li>
<a href = "pwl_interp_1d_test.m">pwl_interp_1d_test.m</a>, calls all the tests;
</li>
<li>
<a href = "pwl_interp_1d_test_output.txt">pwl_interp_1d_test_output.txt</a>,
the output file.
</li>
<li>
<a href = "pwl_interp_1d_test01.m">pwl_interp_1d_test01.m</a>,
plots the basis functions to
the data.
</li>
<li>
<a href = "pwl_interp_1d_test02.m">pwl_interp_1d_test02.m</a>,
plots the piecewise linear basis functions for a given set of nodes.
</li>
</ul>
</p>
<p>
<b>pwl_interp_1d_test01()</b> plots the piecewise linear interpolant to
the data.
<ul>
<li>
<a href = "p01_pwl.png">p01_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p01;
</li>
<li>
<a href = "p02_pwl.png">p02_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p02;
</li>
<li>
<a href = "p03_pwl.png">p03_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p03;
</li>
<li>
<a href = "p04_pwl.png">p04_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p04;
</li>
<li>
<a href = "p05_pwl.png">p05_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p05;
</li>
<li>
<a href = "p06_pwl.png">p06_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p06;
</li>
<li>
<a href = "p07_pwl.png">p07_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p07;
</li>
<li>
<a href = "p08_pwl.png">p08_pwl.png</a>,
a plot of the piecewise linear interpolant for problem p08;
</li>
</ul>
</p>
<p>
<b>pwl_interp_1d_test02()</b> plots the basis functions to
the data.
<ul>
<li>
<a href = "p01_pwl_basis.png">p01_pwl_basis.png</a>,
a plot of the basis functions for problem p01;
</li>
<li>
<a href = "p02_pwl_basis.png">p02_pwl_basis.png</a>,
a plot of the basis functions for problem p02;
</li>
<li>
<a href = "p03_pwl_basis.png">p03_pwl_basis.png</a>,
a plot of the basis functions for problem p03;
</li>
<li>
<a href = "p04_pwl_basis.png">p04_pwl_basis.png</a>,
a plot of the basis functions for problem p04;
</li>
<li>
<a href = "p05_pwl_basis.png">p05_pwl_basis.png</a>,
a plot of the basis functions for problem p05;
</li>
<li>
<a href = "p06_pwl_basis.png">p06_pwl_basis.png</a>,
a plot of the basis functions for problem p06;
</li>
<li>
<a href = "p07_pwl_basis.png">p07_pwl_basis.png</a>,
a plot of the basis functions for problem p07;
</li>
<li>
<a href = "p08_pwl_basis.png">p08_pwl_basis.png</a>,
a plot of the basis functions for problem p08;
</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 modified on 07 August 2012.
</i>
<!-- John Burkardt -->
</body>
</html>