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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Qwt User&apos;s Guide: qwt_math.cpp Source File</title>
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<h1>qwt_math.cpp</h1><pre class="fragment"><div>00001 <span class="comment">/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************</span>
00002 <span class="comment"> * Qwt Widget Library</span>
00003 <span class="comment"> * Copyright (C) 1997   Josef Wilgen</span>
00004 <span class="comment"> * Copyright (C) 2002   Uwe Rathmann</span>
00005 <span class="comment"> * </span>
00006 <span class="comment"> * This library is free software; you can redistribute it and/or</span>
00007 <span class="comment"> * modify it under the terms of the Qwt License, Version 1.0</span>
00008 <span class="comment"> *****************************************************************************/</span>
00009 
00010 <span class="comment">// vim: expandtab</span>
00011 
00012 <span class="preprocessor">#include "<a class="code" href="qwt__math_8h.html">qwt_math.h</a>"</span>
00013 
00019 <span class="keywordtype">double</span> qwtGetMin(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size)
00020 {
00021     <span class="keywordflow">if</span> (size &lt;= 0)
00022        <span class="keywordflow">return</span> 0.0;
00023 
00024     <span class="keywordtype">double</span> rv = array[0];
00025     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 1; i &lt; size; i++)
00026        rv = qwtMin(rv, array[i]);
00027 
00028     <span class="keywordflow">return</span> rv;
00029 }
00030 
00031 
00037 <span class="keywordtype">double</span> qwtGetMax(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size)
00038 {
00039     <span class="keywordflow">if</span> (size &lt;= 0)
00040        <span class="keywordflow">return</span> 0.0;
00041     
00042     <span class="keywordtype">double</span> rv = array[0];
00043     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 1; i &lt; size; i++)
00044        rv = qwtMax(rv, array[i]);
00045 
00046     <span class="keywordflow">return</span> rv;
00047 }
00048 
00049 
00056 <span class="keywordtype">double</span> qwtCeil125( <span class="keywordtype">double</span> x)
00057 {
00058     <span class="keywordflow">if</span> (x == 0.0) 
00059         <span class="keywordflow">return</span> 0.0;
00060 
00061     <span class="keyword">const</span> <span class="keywordtype">double</span> sign = (x &gt; 0) ? 1.0 : -1.0;
00062     <span class="keyword">const</span> <span class="keywordtype">double</span> lx = log10(fabs(x));
00063     <span class="keyword">const</span> <span class="keywordtype">double</span> p10 = floor(lx);
00064 
00065     <span class="keywordtype">double</span> fr = pow(10.0, lx - p10);
00066     <span class="keywordflow">if</span> (fr &lt;=1.0)
00067        fr = 1.0;
00068     <span class="keywordflow">else</span> <span class="keywordflow">if</span> (fr &lt;= 2.0)
00069        fr = 2.0;
00070     <span class="keywordflow">else</span> <span class="keywordflow">if</span> (fr &lt;= 5.0)
00071        fr = 5.0;
00072     <span class="keywordflow">else</span>
00073        fr = 10.0;
00074 
00075     <span class="keywordflow">return</span> sign * fr * pow(10.0, p10);
00076 } 
00077 
00078 
00085 <span class="keywordtype">double</span> qwtFloor125( <span class="keywordtype">double</span> x)
00086 {
00087     <span class="keywordflow">if</span> (x == 0.0) 
00088         <span class="keywordflow">return</span> 0.0;
00089     
00090     <span class="keywordtype">double</span> sign = (x &gt; 0) ? 1.0 : -1.0;
00091     <span class="keyword">const</span> <span class="keywordtype">double</span> lx = log10(fabs(x));
00092     <span class="keyword">const</span> <span class="keywordtype">double</span> p10 = floor(lx);
00093 
00094     <span class="keywordtype">double</span> fr = pow(10.0, lx - p10);
00095     <span class="keywordflow">if</span> (fr &gt;= 10.0)
00096        fr = 10.0;
00097     <span class="keywordflow">else</span> <span class="keywordflow">if</span> (fr &gt;= 5.0)
00098        fr = 5.0;
00099     <span class="keywordflow">else</span> <span class="keywordflow">if</span> (fr &gt;= 2.0)
00100        fr = 2.0;
00101     <span class="keywordflow">else</span>
00102        fr = 1.0;
00103 
00104     <span class="keywordflow">return</span> sign * fr * pow(10.0, p10);
00105 } 
00106 
00107 
00119 <span class="keywordtype">int</span> qwtChkMono(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size)
00120 {
00121     <span class="keywordflow">if</span> (size &lt; 2) 
00122         <span class="keywordflow">return</span> 0;
00123     
00124     <span class="keywordtype">int</span> rv = <a class="code" href="qwt__math_8h.html#a30">qwtSign</a>(array[1] - array[0]);
00125     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 1; i &lt; size - 1; i++)
00126     {
00127         <span class="keywordflow">if</span> ( <a class="code" href="qwt__math_8h.html#a30">qwtSign</a>(array[i+1] - array[i]) != rv )
00128         {
00129             rv = 0;
00130             <span class="keywordflow">break</span>;
00131         }
00132     }
00133     <span class="keywordflow">return</span> rv;
00134 }
00135 
00141 <span class="keywordtype">void</span> qwtTwistArray(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size)
00142 {
00143     <span class="keyword">const</span> <span class="keywordtype">int</span> s2 = size / 2;
00144     
00145     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i=0; i &lt; s2; i++)
00146     {
00147         <span class="keyword">const</span> <span class="keywordtype">int</span> itmp = size - 1 - i;
00148         <span class="keyword">const</span> <span class="keywordtype">double</span> dtmp = array[i];
00149         array[i] = array[itmp];
00150         array[itmp] = dtmp;
00151     }
00152 }
00153 
00161 <span class="keywordtype">void</span> qwtLinSpace(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size, <span class="keywordtype">double</span> xmin, <span class="keywordtype">double</span> xmax)
00162 {
00163     <span class="keywordflow">if</span> (size &lt;= 0)
00164         <span class="keywordflow">return</span>;
00165 
00166     <span class="keyword">const</span> <span class="keywordtype">int</span> imax = size -1;
00167 
00168     array[0] = xmin;
00169     array[imax] = xmax;
00170 
00171     <span class="keyword">const</span> <span class="keywordtype">double</span> step = (xmax - xmin) / double(imax);
00172     <span class="keyword">const</span> <span class="keywordtype">double</span> tiny = 1e-6;
00173 
00174     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 1; i &lt; imax; i++)
00175     {
00176        array[i] = xmin + double(i) * step;
00177        <span class="keywordflow">if</span> (fabs(array[i]) &lt; tiny*fabs(step))
00178           array[i] = step*floor(array[i]/step + tiny/2);
00179     }
00180 }
00181 
00189 <span class="keywordtype">void</span> qwtLogSpace(<span class="keywordtype">double</span> *array, <span class="keywordtype">int</span> size, <span class="keywordtype">double</span> xmin, <span class="keywordtype">double</span> xmax)
00190 {
00191     <span class="keywordflow">if</span> ((xmin &lt;= 0.0) || (xmax &lt;= 0.0) || (size &lt;= 0))
00192        <span class="keywordflow">return</span>;
00193 
00194     <span class="keyword">const</span> <span class="keywordtype">int</span> imax = size -1;
00195 
00196     array[0] = xmin;
00197     array[imax] = xmax;
00198 
00199     <span class="keyword">const</span> <span class="keywordtype">double</span> lxmin = log(xmin);
00200     <span class="keyword">const</span> <span class="keywordtype">double</span> lxmax = log(xmax);
00201     <span class="keyword">const</span> <span class="keywordtype">double</span> lstep = (lxmax - lxmin) / double(imax);
00202 
00203     <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 1; i &lt; imax; i++)
00204        array[i] = exp(lxmin + <span class="keywordtype">double</span>(i) * lstep);
00205 }
</div></pre><hr size="1"><address style="align: right;"><small>Generated on Tue Nov 16 21:12:20 2004 for Qwt User's Guide by
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