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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Qwt User's Guide: QwtSpline Class Reference</title>
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<!-- Generated by Doxygen 1.3.8 -->
<div class="qindex"><a class="qindex" href="index.html">Main Page</a> | <a class="qindex" href="hierarchy.html">Class Hierarchy</a> | <a class="qindex" href="classes.html">Alphabetical List</a> | <a class="qindex" href="annotated.html">Class List</a> | <a class="qindex" href="files.html">File List</a> | <a class="qindex" href="functions.html">Class Members</a> | <a class="qindex" href="globals.html">File Members</a> | <a class="qindex" href="pages.html">Related Pages</a></div>
<h1>QwtSpline Class Reference</h1><a href="class_qwt_spline-members.html">List of all members.</a><hr><a name="_details"></a><h2>Detailed Description</h2>
A class for spline interpolation.
<p>
The QwtSpline class is used for cubical spline interpolation. Two types of splines, natural and periodic, are supported.<p>
<dl compact><dt><b>Usage:</b></dt><dd><ol>
<li>
First call <a class="el" href="class_qwt_spline.html#a3">QwtSpline::recalc()</a> to determine the spline coefficients for a tabulated function y(x). </li>
<li>
After the coefficients have been set up, the interpolated function value for an argument x can be determined by calling <a class="el" href="class_qwt_spline.html#a2">QwtSpline::value()</a>. </li>
</ol>
In order to save storage space, QwtSpline can be advised not to buffer the contents of x and y. This means that the arrays have to remain valid and unchanged for the interpolation to work properly. This can be achieved by calling <a class="el" href="class_qwt_spline.html#a5">QwtSpline::copyValues()</a>.</dd></dl>
<dl compact><dt><b>Example:</b></dt><dd><div class="fragment"><pre><span class="preprocessor">#include<qwt_spline.h></span>
<span class="preprocessor">#include<iostream.h></span>
<a class="code" href="class_qwt_spline.html">QwtSpline</a> s;
<span class="keywordtype">double</span> x[30], y[30], xInter[300], yInter[300];
<span class="keywordtype">int</span> i;
<span class="keywordflow">for</span>(i=0;i<30;i++) <span class="comment">// fill up x[] and y[]</span>
cin >> x[i] >> y[i];
<span class="keywordflow">if</span> (s.<a class="code" href="class_qwt_spline.html#a3">recalc</a>(x,y,30,0) == 0) <span class="comment">// build natural spline</span>
{
<span class="keywordflow">for</span>(i=0;i<300;i++) <span class="comment">// interpolate</span>
{
xInter[i] = x[0] + double(i) * (x[29] - x[0]) / 299.0;
yInter[i] = s.<a class="code" href="class_qwt_spline.html#a2">value</a>( xInter[i] );
}
do_something(xInter, yInter, 300);
}
<span class="keywordflow">else</span>
cerr << <span class="stringliteral">"Uhhh...\n"</span>;
</pre></div></dd></dl>
<p>
Definition at line <a class="el" href="qwt__spline_8h-source.html#l00063">63</a> of file <a class="el" href="qwt__spline_8h-source.html">qwt_spline.h</a>.<table border=0 cellpadding=0 cellspacing=0>
<tr><td></td></tr>
<tr><td colspan=2><br><h2>Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top> </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a0">QwtSpline</a> ()</td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top> </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a1">~QwtSpline</a> ()</td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>double </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a2">value</a> (double x) const</td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>int </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a3">recalc</a> (double *x, double *y, int n, int periodic=0)</td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>int </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a4">recalc</a> (const QwtArray< double > &x, const QwtArray< double > &y, int periodic=0)</td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>void </td><td class="memItemRight" valign=bottom><a class="el" href="class_qwt_spline.html#a5">copyValues</a> (int tf=1)</td></tr>
</table>
<hr><h2>Constructor & Destructor Documentation</h2>
<a class="anchor" name="a0" doxytag="QwtSpline::QwtSpline" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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<td class="md" nowrap valign="top"> QwtSpline::QwtSpline </td>
<td class="md" valign="top">( </td>
<td class="mdname1" valign="top" nowrap> </td>
<td class="md" valign="top"> ) </td>
<td class="md" nowrap></td>
</tr>
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</td>
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<td>
</td>
<td>
<p>
CTOR.
<p>
Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00031">31</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>. </td>
</tr>
</table>
<a class="anchor" name="a1" doxytag="QwtSpline::~QwtSpline" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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<td class="mdRow">
<table cellpadding="0" cellspacing="0" border="0">
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<td class="md" nowrap valign="top"> QwtSpline::~<a class="el" href="class_qwt_spline.html">QwtSpline</a> </td>
<td class="md" valign="top">( </td>
<td class="mdname1" valign="top" nowrap> </td>
<td class="md" valign="top"> ) </td>
<td class="md" nowrap></td>
</tr>
</table>
</td>
</tr>
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<table cellspacing=5 cellpadding=0 border=0>
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<td>
</td>
<td>
<p>
DTOR.
<p>
Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00068">68</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>. </td>
</tr>
</table>
<hr><h2>Member Function Documentation</h2>
<a class="anchor" name="a5" doxytag="QwtSpline::copyValues" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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<td class="md" nowrap valign="top"> void QwtSpline::copyValues </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">int </td>
<td class="mdname1" valign="top" nowrap> <em>tf</em> = <code>1</code> </td>
<td class="md" valign="top"> ) </td>
<td class="md" nowrap></td>
</tr>
</table>
</td>
</tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
<tr>
<td>
</td>
<td>
<p>
Advise <a class="el" href="class_qwt_spline.html#a3">recalc()</a> to buffer the tabulated function or switch off internal buffering.
<p>
By default, QwtSpline maintains an internal copy of the tabulated function given as *x and *y arguments of <a class="el" href="class_qwt_spline.html#a3">QwtSpline::recalc()</a>.<p>
If <a class="el" href="class_qwt_spline.html#a5">QwtSpline::copyValues()</a> is called with zero argument, subsequent calls to <a class="el" href="class_qwt_spline.html#a3">QwtSpline::recalc()</a> will not buffer these values anymore and just store the pointers instead. The <a class="el" href="class_qwt_spline.html#a2">QwtSpline::value()</a> function will then silently assume that these pointers remained valid and that the contents of the arrays have not been changed since the last <a class="el" href="class_qwt_spline.html#a3">QwtSpline::recalc()</a>.<p>
If called with no or nonzero argument, any following <a class="el" href="class_qwt_spline.html#a3">QwtSpline::recalc()</a> calls will use the internal buffer.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td></td><td valign=top><em>tf</em> </td><td>if nonzero, the function table will be buffered </td></tr>
</table>
</dl>
<dl compact><dt><b>Warning:</b></dt><dd><a class="el" href="class_qwt_spline.html#a5">copyValues()</a> resets all the contents of QwtSpline. A subsequent <a class="el" href="class_qwt_spline.html#a3">recalc()</a> will be necessary. </dd></dl>
Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00061">61</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>. </td>
</tr>
</table>
<a class="anchor" name="a4" doxytag="QwtSpline::recalc" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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<td class="md" nowrap valign="top"> int QwtSpline::recalc </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">const QwtArray< double > & </td>
<td class="mdname" nowrap> <em>x</em>, </td>
</tr>
<tr>
<td class="md" nowrap align="right"></td>
<td></td>
<td class="md" nowrap>const QwtArray< double > & </td>
<td class="mdname" nowrap> <em>y</em>, </td>
</tr>
<tr>
<td class="md" nowrap align="right"></td>
<td></td>
<td class="md" nowrap>int </td>
<td class="mdname" nowrap> <em>periodic</em> = <code>0</code></td>
</tr>
<tr>
<td></td>
<td class="md">) </td>
<td class="md" colspan="2"></td>
</tr>
</table>
</td>
</tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
<tr>
<td>
</td>
<td>
<p>
re-calculate the spline coefficients
<p>
Depending on the value of <em>periodic</em>, this function will determine the coefficients for a natural or a periodic spline and store them internally. It also buffers the values of x and y, which are needed for the interpolation (See <a class="el" href="class_qwt_spline.html#a2">QwtSpline::value()</a>). <dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td></td><td valign=top><em>x</em> </td><td>QwtArray<double> of points </td></tr>
<tr><td></td><td valign=top><em>y</em> </td><td>QwtArray<double> of points </td></tr>
<tr><td></td><td valign=top><em>periodic</em> </td><td>if non-zero, calculate periodic spline </td></tr>
</table>
</dl>
<dl compact><dt><b>Returns:</b></dt><dd><dl>
<dt>0</dt>
<dd>successful </dd>
<dt>Qwt::ErrMono<dd>Sequence of x values is not strictly monotone increasing </dt>
<dd></dd>
<dt>Qwt::ErrNoMem<dd>Couldn't allocate memory </dt>
<dd></dd>
</dl>
</dd></dl>
<dl compact><dt><b>Warning:</b></dt><dd>The sequence of x (but not y) values has to be strictly monotone increasing, which means <code>x[0] < x[1] < .... < x[n-1]</code>. If this is not the case, the function will return an error. </dd></dl>
Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00206">206</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>.
<p>
References <a class="el" href="qwt__spline_8cpp-source.html#l00127">recalc()</a>. </td>
</tr>
</table>
<a class="anchor" name="a3" doxytag="QwtSpline::recalc" ></a><p>
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<td class="md" nowrap valign="top"> int QwtSpline::recalc </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">double * </td>
<td class="mdname" nowrap> <em>x</em>, </td>
</tr>
<tr>
<td class="md" nowrap align="right"></td>
<td></td>
<td class="md" nowrap>double * </td>
<td class="mdname" nowrap> <em>y</em>, </td>
</tr>
<tr>
<td class="md" nowrap align="right"></td>
<td></td>
<td class="md" nowrap>int </td>
<td class="mdname" nowrap> <em>n</em>, </td>
</tr>
<tr>
<td class="md" nowrap align="right"></td>
<td></td>
<td class="md" nowrap>int </td>
<td class="mdname" nowrap> <em>periodic</em> = <code>0</code></td>
</tr>
<tr>
<td></td>
<td class="md">) </td>
<td class="md" colspan="2"></td>
</tr>
</table>
</td>
</tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
<tr>
<td>
</td>
<td>
<p>
re-calculate the spline coefficients
<p>
Depending on the value of <em>periodic</em>, this function will determine the coefficients for a natural or a periodic spline and store them internally. By default, it also buffers the values of x and y, which are needed for the interpolation (See <a class="el" href="class_qwt_spline.html#a2">QwtSpline::value()</a>). In order to save memory, this last behaviour may be changed with the <a class="el" href="class_qwt_spline.html#a5">QwtSpline::copyValues()</a> function.<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
<table border="0" cellspacing="2" cellpadding="0">
<tr><td></td><td valign=top><em>x</em> </td><td></td></tr>
<tr><td></td><td valign=top><em>y</em> </td><td>points </td></tr>
<tr><td></td><td valign=top><em>n</em> </td><td>number of points </td></tr>
<tr><td></td><td valign=top><em>periodic</em> </td><td>if non-zero, calculate periodic spline </td></tr>
</table>
</dl>
<dl compact><dt><b>Returns:</b></dt><dd><dl>
<dt>0</dt>
<dd>successful </dd>
<dt>Qwt::ErrMono<dd>Sequence of x values is not strictly monotone increasing </dt>
<dd></dd>
<dt>Qwt::ErrNoMem<dd>Couldn't allocate memory </dt>
<dd></dd>
</dl>
</dd></dl>
<dl compact><dt><b>Warning:</b></dt><dd>The sequence of x (but not y) values has to be strictly monotone increasing, which means <code>x[0] < x[1] < .... < x[n-1]</code>. If this is not the case, the function will return an error. </dd></dl>
Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00127">127</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>.
<p>
Referenced by <a class="el" href="qwt__curve_8cpp-source.html#l00583">QwtCurve::drawSpline()</a>, and <a class="el" href="qwt__spline_8cpp-source.html#l00206">recalc()</a>. </td>
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<a class="anchor" name="a2" doxytag="QwtSpline::value" ></a><p>
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<td class="md" nowrap valign="top"> double QwtSpline::value </td>
<td class="md" valign="top">( </td>
<td class="md" nowrap valign="top">double </td>
<td class="mdname1" valign="top" nowrap> <em>x</em> </td>
<td class="md" valign="top"> ) </td>
<td class="md" nowrap> const</td>
</tr>
</table>
</td>
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<table cellspacing=5 cellpadding=0 border=0>
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<td>
</td>
<td>
<p>
Calculate the interpolated function value corresponding to a given argument x. Definition at line <a class="el" href="qwt__spline_8cpp-source.html#l00018">18</a> of file <a class="el" href="qwt__spline_8cpp-source.html">qwt_spline.cpp</a>.
<p>
Referenced by <a class="el" href="qwt__curve_8cpp-source.html#l00583">QwtCurve::drawSpline()</a>. </td>
</tr>
</table>
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