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<h3 class="section">26.3 Interpolation Types</h3>
<p>The interpolation library provides five interpolation types:
<div class="defun">
— Interpolation Type: <b>gsl_interp_linear</b><var><a name="index-gsl_005finterp_005flinear-2082"></a></var><br>
<blockquote><p><a name="index-linear-interpolation-2083"></a>Linear interpolation. This interpolation method does not require any
additional memory.
</p></blockquote></div>
<div class="defun">
— Interpolation Type: <b>gsl_interp_polynomial</b><var><a name="index-gsl_005finterp_005fpolynomial-2084"></a></var><br>
<blockquote><p><a name="index-polynomial-interpolation-2085"></a>Polynomial interpolation. This method should only be used for
interpolating small numbers of points because polynomial interpolation
introduces large oscillations, even for well-behaved datasets. The
number of terms in the interpolating polynomial is equal to the number
of points.
</p></blockquote></div>
<div class="defun">
— Interpolation Type: <b>gsl_interp_cspline</b><var><a name="index-gsl_005finterp_005fcspline-2086"></a></var><br>
<blockquote><p><a name="index-cubic-splines-2087"></a>Cubic spline with natural boundary conditions. The resulting curve is
piecewise cubic on each interval, with matching first and second
derivatives at the supplied data-points. The second derivative is
chosen to be zero at the first point and last point.
</p></blockquote></div>
<div class="defun">
— Interpolation Type: <b>gsl_interp_cspline_periodic</b><var><a name="index-gsl_005finterp_005fcspline_005fperiodic-2088"></a></var><br>
<blockquote><p>Cubic spline with periodic boundary conditions. The resulting curve
is piecewise cubic on each interval, with matching first and second
derivatives at the supplied data-points. The derivatives at the first
and last points are also matched. Note that the last point in the
data must have the same y-value as the first point, otherwise the
resulting periodic interpolation will have a discontinuity at the
boundary.
</blockquote></div>
<div class="defun">
— Interpolation Type: <b>gsl_interp_akima</b><var><a name="index-gsl_005finterp_005fakima-2089"></a></var><br>
<blockquote><p><a name="index-Akima-splines-2090"></a>Non-rounded Akima spline with natural boundary conditions. This method
uses the non-rounded corner algorithm of Wodicka.
</p></blockquote></div>
<div class="defun">
— Interpolation Type: <b>gsl_interp_akima_periodic</b><var><a name="index-gsl_005finterp_005fakima_005fperiodic-2091"></a></var><br>
<blockquote><p>Non-rounded Akima spline with periodic boundary conditions. This method
uses the non-rounded corner algorithm of Wodicka.
</p></blockquote></div>
<p>The following related functions are available:
<div class="defun">
— Function: const char * <b>gsl_interp_name</b> (<var>const gsl_interp * interp</var>)<var><a name="index-gsl_005finterp_005fname-2092"></a></var><br>
<blockquote><p>This function returns the name of the interpolation type used by <var>interp</var>.
For example,
<pre class="example"> printf ("interp uses '%s' interpolation.\n",
gsl_interp_name (interp));
</pre>
<p class="noindent">would print something like,
<pre class="example"> interp uses 'cspline' interpolation.
</pre>
</blockquote></div>
<div class="defun">
— Function: unsigned int <b>gsl_interp_min_size</b> (<var>const gsl_interp * interp</var>)<var><a name="index-gsl_005finterp_005fmin_005fsize-2093"></a></var><br>
<blockquote><p>This function returns the minimum number of points required by the
interpolation type of <var>interp</var>. For example, Akima spline interpolation
requires a minimum of 5 points.
</p></blockquote></div>
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