MATLAB教程_matlab_其他_其他下载-pudn.com

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/bg1.jpg"><div class="c x1 y1 w2 h2"><div class="t m0 x2 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">下载</div><div class="t m0 x3 h4 y3 ff2 fs1 fc1 sc0 ls0 ws0">第<span class="_ _0"></span><span class="ff3">1<span class="_ _0"></span></span>章<span class="_ _1"> </span><span class="ff3 ws1">M AT L A B<span class="_"> </span></span>是什么</div><div class="t m0 x4 h5 y4 ff1 fs2 fc0 sc0 ls0 ws0">没有<span class="_ _0"></span><span class="ff4 ws2">M AT L A B<span class="_ _0"></span></span><span class="ls1">就没有乐趣。</span></div><div class="t m0 x5 h5 y5 ff4 fs2 fc0 sc0 ls2 ws0">Nachtigal, M. N., Reddy, S. C., Trefethen, L.N.(1990)<span class="_ _0"></span><span class="ff1 ls0">。</span></div><div class="t m0 x6 h6 y6 ff1 fs2 fc0 sc0 ls3 ws0">不对称矩阵迭代有多快？</div><div class="t m0 x7 h5 y7 ff1 fs2 fc0 sc0 ls4 ws0">关于迭代方法的<span class="_ _2"></span><span class="ff4 ls5">Copper Mountain<span class="_ _3"></span></span><span class="ls1">会议论文集，</span></div><div class="t m0 x8 h5 y8 ff4 fs2 fc0 sc0 ls6 ws0">Copper Mountain CO, 1-5,1990<span class="_ _3"></span><span class="ff1 ls0">年<span class="_ _3"></span><span class="ff4">4<span class="_ _3"></span></span>月。</span></div><div class="t m0 x9 h7 y9 ff3 fs3 fc1 sc0 ls7 ws0">1.1 MA<span class="_ _4"></span><span class="ls0 ws3">T L A B<span class="ff5 ws0">能做什么</span></span></div><div class="t m0 x4 h5 ya ff4 fs2 fc0 sc0 ls0 ws4">M AT L A B<span class="_"> </span><span class="ff6 ls8 ws0">是一个可视化的计算程序，被广泛地使用于从个人计算机到超级计算机范围内</span></div><div class="t m0 x9 h6 yb ff6 fs2 fc0 sc0 ls9 ws0">的各种计算机上。</div><div class="t m0 x4 h5 yc ff4 fs2 fc0 sc0 ls0 ws4">M AT L A B<span class="ff6 ls8 ws0">包括命令控制、可编程，有上百个预先定义好的命令和函数。这些函数能通过</span></div><div class="t m0 x9 h6 yd ff6 fs2 fc0 sc0 lsa ws0">用户自定义函数进一步扩展。</div><div class="t m0 x4 h5 ye ff4 fs2 fc0 sc0 ls0 ws5">M AT L A B<span class="_"> </span><span class="ff6 lsb ws0">有许多强有力的命令。例如，<span class="_ _5"> </span></span>M AT L A B<span class="_"> </span><span class="ff6 lsc ws0">能够用一个单一的命令求解线性系统，</span></div><div class="t m0 x9 h6 yf ff6 fs2 fc0 sc0 lsa ws0">能完成大量的高级矩阵处理。</div><div class="t m0 x4 h5 y10 ff4 fs2 fc0 sc0 ls0 ws2">M AT L A B<span class="_ _3"></span><span class="ff6 lsd ws0">有强有力的二维、三维图形工具。</span></div><div class="t m0 x4 h5 y11 ff4 fs2 fc0 sc0 ls0 ws6">M AT L A B<span class="_ _2"></span><span class="ff6 lse ws0">能与其他程序一起使用。例如，<span class="_ _5"> </span></span><span class="ws7">M AT L A B<span class="ff6 lse ws0">的图形功能，可以在一个<span class="_ _6"> </span></span><span class="ws8">F O RT R A N</span></span></div><div class="t m0 x9 h6 y12 ff6 fs2 fc0 sc0 lsf ws0">程序中完成可视化计算。</div><div class="t m0 x4 h5 y13 ff4 fs2 fc0 sc0 ls0 ws9">2 5<span class="_"> </span><span class="ff6 ws0">个不同的<span class="_ _2"></span></span><span class="ws2">M AT L A B<span class="_ _3"></span><span class="ff6 lsd ws0">工具箱可应用于特殊的应用领域。</span></span></div><div class="t m0 x4 h5 y14 ff4 fs2 fc0 sc0 ls0 ws2">M AT L A B<span class="_ _3"></span><span class="ff6 ls10 ws0">在以下的领域里解决各种问题是一个十分有效的工具：</span></div><div class="t m0 x4 h5 y15 ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6 ls9">工业研究与开发。</span></div><div class="t m0 x4 h5 y16 ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6 ls10">数学教学，特别是线性代数。所有基本概念都能涉及。</span></div><div class="t m0 x4 h5 y17 ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6 ls11">在数值分析和科学计算方面的教学与研究。能够详细地研究和比较各种算法。</span></div><div class="t m0 x4 h5 y18 ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6 ls11">在诸如电子学、控制理论和物理学等工程和科学学科方面的教学与研究。</span></div><div class="t m0 x4 h5 y19 ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6 ls11">在诸如经济学、化学和生物学等有计算问题的所有其他领域中的教学与研究。</span></div><div class="t m0 x4 h5 y1a ff4 fs2 fc0 sc0 ls0 ws0">• <span class="_ _0"></span><span class="ff6">在<span class="_ _3"></span></span><span class="wsa">M AT L A B</span><span class="ff6 ls12">中创建的组是矩阵，<span class="_ _7"></span></span><span class="wsa">M AT L A B</span><span class="ff6 ls13">的名字取自矩阵实验室<span class="_ _7"></span></span><span class="ws9">( M A<span class="_ _4"></span><span class="ls14 ws0">Trix LABoratory)<span class="ff6 ls0">。</span></span></span></div><div class="t m0 x9 h7 y1b ff3 fs3 fc1 sc0 ls15 ws0">1.2 MA<span class="_ _4"></span><span class="ls0 ws3">T L A B<span class="_"> </span><span class="ff5 ws0">实例</span></span></div><div class="t m0 x4 h5 y1c ff6 fs2 fc0 sc0 ls16 ws0">本节中的实例恰当而简洁地展示了<span class="_ _8"> </span><span class="ff4 ls0 wsb">M AT L A B<span class="_"> </span></span><span class="ls17">能做什么。在一些实例中给出了完整的</span></div><div class="t m0 x9 h5 y1d ff4 fs2 fc0 sc0 ls0 wsa">M AT L A B<span class="_"> </span><span class="ff6 ls18 ws0">命令；而在另一些实例中，为简化仅给出部分命令。</span></div><div class="t m0 x4 h5 y1e ff6 fs2 fc0 sc0 ls19 ws0">在本书中出现的<span class="_ _9"> </span><span class="ff4 ls0 wsc">M AT L A B<span class="_"> </span></span><span class="ls1a">代码用的是一种特殊的字体以区别于书中别的文字。</span></div><div class="t m0 x9 h5 y1f ff4 fs2 fc0 sc0 ls0 wsd">M AT L A B<span class="_"> </span><span class="ff6 ls1b ws0">的输出是斜体字，即：我们输给<span class="_ _a"> </span></span><span class="wse">M AT L A B<span class="_"> </span><span class="ff6 ls1c ws0">的命令是正体；<span class="_ _b"> </span></span>M AT L A B<span class="_"> </span><span class="ff6 ls16 ws0">给出的输出答</span></span></div><div class="t m0 x9 h6 y20 ff6 fs2 fc0 sc0 ls1d ws0">案是斜体。</div><div class="t m0 x4 h5 y21 ff6 fs2 fc0 sc0 ls1e ws0">百分符号％在<span class="_ _7"></span><span class="ff4 ls0 ws4">M AT L A B<span class="_ _0"></span></span><span class="ls1f">中用做注释符号，在本书中全部都是这样使用。采用的其他表示</span></div><div class="t m0 x9 h6 y22 ff6 fs2 fc0 sc0 ls20 ws0">方法是：数量和预定义函数用斜体字，矩阵、向量和用户自定义函数用黑体字。矩阵用大写</div></div></div><div class="pi" data-data='{"ctm":[1.860465,0.000000,0.000000,1.860465,0.000000,0.000000]}'></div></div> </body> </html>

<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/bg2.jpg"><div class="t m0 xa h6 y23 ff6 fs2 fc0 sc0 ls21 ws0">字母开头命名，而向量以小写字母开头。细胞矩阵是如同矩阵或向量的概念，也采用黑体字，</div><div class="t m0 xa h6 y24 ff6 fs2 fc0 sc0 ls22 ws0">其结构和对象也是如此。在命令表中，用斜体字表示那些可选的函数参数。例如，</div><div class="t m0 xa h5 y25 ff4 fs2 fc0 sc0 ls0 ws9">c o m m a n d (<span class="ff7 ls23 ws0">parl, <span class="_ _c"></span><span class="ff8 ls0 wsf">p a r<span class="_"> </span><span class="ff7">2<span class="_"> </span><span class="ff4 ws10">)<span class="_ _3"></span><span class="ff6 ws0">，参数<span class="_ _2"></span></span></span>p a r 1<span class="_"> </span><span class="ff6 ls4 ws0">总是需要的，而<span class="_ _2"></span></span></span>p a r<span class="ff7">2<span class="_"> </span><span class="ff6 ws0">是可选的。</span></span></span></span></div><div class="t m0 xa h6 y26 ff5 fs2 fc0 sc0 ls0 ws0">■<span class="_ _5"> </span>例<span class="_ _3"></span><span class="ff3 ls24">1.1 <span class="_ _3"></span></span><span class="ls4">二维和三维函数</span></div><div class="t m0 xb h5 y27 ff4 fs2 fc0 sc0 ls0 ws11">M AT L A B<span class="_"> </span><span class="ff6 ls25 ws0">能用于计算，并以二维和三维图形显示各种函数。在<span class="_ _d"> </span></span>M AT L A B<span class="_"> </span><span class="ff6 ls26 ws0">函数中包括了所</span></div><div class="t m0 xa h6 y28 ff6 fs2 fc0 sc0 ls27 ws0">有主要的数学函数和大量的高级函数。</div><div class="t m0 xb h5 y29 ff4 fs2 fc0 sc0 ls0 ws0">(a) <span class="_ _2"></span><span class="ff6">用简短的<span class="_ _2"></span></span><span class="ws2">M AT L A B<span class="_ _3"></span></span><span class="ff6 ls9">命令计算并绘制在<span class="_ _7"></span><span class="ff4">0<span class="_ _3"></span></span><span class="ls0">≤<span class="_ _3"></span><span class="ff9">x</span>≤<span class="_ _3"></span></span></span>6<span class="_ _3"></span><span class="ff6">范围内的<span class="_ _2"></span></span><span class="ws9">s i n ( 2<span class="_"> </span><span class="ff9">x<span class="_ _0"></span></span>)</span><span class="ff6">、<span class="_ _3"></span></span><span class="ws9">s i n<span class="_ _0"></span><span class="ff9">x</span></span></div><div class="t m0 xc h8 y2a ff4 fs4 fc0 sc0 ls0 ws9">2</div><div class="t m0 xd h5 y29 ff6 fs2 fc0 sc0 ls0 ws0">和<span class="_ _3"></span><span class="ff4 ws9">s i n</span></div><div class="t m0 xe h8 y2a ff4 fs4 fc0 sc0 ls0 ws9">2</div><div class="t m0 xf h9 y29 ff9 fs2 fc0 sc0 ls0 ws9">x<span class="ff6 ws0">。</span></div><div class="t m0 xb ha y2b ff7 fs5 fc0 sc0 ls0 ws12">x = l i n s p a c e ( 0 , 6 ) ;<span class="_ _8"> </span><span class="ws0">% <span class="_ _3"></span><span class="ff6">创建一个向量<span class="_ _7"> </span></span>x<span class="_ _0"></span><span class="ff6">。</span></span></div><div class="t m0 xb hb y2c ff7 fs5 fc0 sc0 ls0 ws12">y 1 = s i n ( 2</div><div class="t m0 x10 hc y2d ff4 fs5 fc0 sc0 ls0 ws13">*</div><div class="t m0 x11 ha y2c ff7 fs5 fc0 sc0 ls0 ws12">x ) ;<span class="_ _e"> </span><span class="ws0">% <span class="_ _0"></span><span class="ff6">向量<span class="_ _3"></span></span></span>y 1<span class="_"> </span><span class="ff6 ws0">等于<span class="_ _3"></span><span class="ff7">x<span class="_ _3"></span></span>坐标上某一<span class="_ _2"></span><span class="ff7">x<span class="_ _3"></span></span>的</span>s i n ( 2 x )<span class="_ _0"></span><span class="ff6 ws0">值。</span></div><div class="t m0 xb ha y2e ff7 fs5 fc0 sc0 ls0 ws12">y 2 = s i n ( x . ^ 2 ) ;<span class="_ _f"> </span><span class="ws0">% <span class="_ _2"></span><span class="ff6">向量</span></span>y 2<span class="_"> </span><span class="ff6 ws0">等于<span class="_ _3"></span></span>s i n ( x . ^ 2 )<span class="_ _0"></span><span class="ff6 ws0">，同上。</span></div><div class="t m0 xb ha y2f ff7 fs5 fc0 sc0 ls0 ws12">y 3 = ( s i n ( x ) ) . ^ 2 ;<span class="_ _10"> </span><span class="ws0">% <span class="_ _2"></span><span class="ff6">向量</span></span>y 3<span class="_"> </span><span class="ff6 ws0">等于<span class="_ _3"></span></span>( s i n ( x ) ) . ^ 2<span class="_ _0"></span><span class="ff6 ws0">，同上。</span></div><div class="t m0 xb hd y30 ff6 fs2 fc0 sc0 ls0 ws0">命令<span class="_ _11"></span><span class="ff7 ws14">p l o t ( x , y 1 )</span><span class="ls28">绘制向量<span class="_ _2"></span></span><span class="ffa ws15">y 1<span class="_"> </span></span>，<span class="_ _0"></span><span class="ffa ws15">y 1<span class="_"> </span></span><span class="ls28">作为向量<span class="_ _11"></span><span class="ffa">x<span class="_ _0"></span></span><span class="ls29">的一个函数，<span class="_ _7"></span></span></span><span class="ff7 ws14">p l o t<span class="_"> </span></span><span class="ls1e">命令的定义可参见第<span class="_ _b"> </span></span><span class="ff4 ws15">1 3</span></div><div class="t m0 xa h5 y31 ff6 fs2 fc0 sc0 ls2a ws0">章。由此能够很容易地在一个图上绘制<span class="_ _12"> </span><span class="ff4 ls0 ws16">s i n ( 2<span class="ff9">x<span class="_ _0"></span></span>)</span><span class="ls0">、<span class="ff4 ws16">s i n (<span class="_ _0"></span><span class="ff9">x</span></span></span></div><div class="t m0 x12 h8 y32 ff4 fs4 fc0 sc0 ls0 ws16">2</div><div class="t m0 x13 h5 y31 ff4 fs2 fc0 sc0 ls0 ws16">)<span class="ff6 ws0">和</span>s i n</div><div class="t m0 x14 h8 y32 ff4 fs4 fc0 sc0 ls0 ws16">2</div><div class="t m0 x15 h5 y31 ff9 fs2 fc0 sc0 ls0 ws16">x<span class="ff6 ls2b ws0">的曲线并正确地标记它们<span class="_ _7"></span><span class="ff4">(</span><span class="ls0">图<span class="_ _3"></span></span></span><span class="ff4">1 - 1 )<span class="_"> </span><span class="ff6 ws0">。</span></span></div><div class="t m0 x16 he y33 ff6 fs6 fc1 sc0 ls0 ws0">图<span class="ff4 ls24">1-1 <span class="_ _3"></span></span><span class="ls12">同一图上的三条曲线</span></div><div class="t m0 xb h5 y34 ff4 fs2 fc0 sc0 ls2c ws0">(b) <span class="_ _11"></span><span class="ff6 ls2d">两个变量的函数需要用三维来恰当地图示，<span class="_ _13"></span><span class="ff4 ls0 ws17">M AT L A B<span class="_ _4"></span><span class="ff6 ls2e ws0">能够给出很好的三维图。在图<span class="_ _14"></span><span class="ff4 ls0 ws18">1 - 2<span class="_"> </span><span class="ff6 ws0">中，用</span></span></span></span></span></div><div class="t m0 xa h5 y35 ff6 fs2 fc0 sc0 ls2f ws0">四个不同的方法展示了函数<span class="_ _15"></span><span class="ff9">f<span class="_ _16"></span><span class="ff4">(<span class="_ _4"></span><span class="ff9">x<span class="ff4 ls0">, <span class="_ _17"></span><span class="ff9">y<span class="_ _4"></span><span class="ff4 ls30">) = cos (<span class="_ _4"></span><span class="ff9">x<span class="ff4">)<span class="_ _4"></span><span class="ff6 ls0">·<span class="_ _4"></span><span class="ff4 ls31">sin (<span class="_ _4"></span><span class="ff9">y<span class="_ _4"></span><span class="ff4">)<span class="ff6 ls2f">的图形：左上图用<span class="_ _18"></span><span class="ff7 ls0 ws19">s u r f<span class="_"> </span><span class="ff6 ws0">命令和<span class="_ _19"></span><span class="ff7 ls32">shading interp<span class="_ _1a"> </span><span class="ff6 ls0">；右</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></div><div class="t m0 xa h5 y36 ff6 fs2 fc0 sc0 ls0 ws0">上图用<span class="_ _19"></span><span class="ff7 ws19">m e s h<span class="_"> </span><span class="ff6 ls33 ws0">；左下图用<span class="_ _19"></span><span class="ff7 ls0 ws19">w a t e r f a l l<span class="_"> </span><span class="ff6 ls34 ws0">以及右下图用<span class="_ _1b"></span><span class="ff7 ls0 ws19">c o n t o u r<span class="_"> </span><span class="ff6 ls35 ws0">。关于图像命令的详细信息可参见第<span class="_ _1c"></span><span class="ff4 ls0 ws1a">1 3<span class="_"> </span><span class="ff6 ws0">章。</span></span></span></span></span></span></span></span></div><div class="t m0 x17 he y37 ff6 fs6 fc1 sc0 ls0 ws0">图<span class="_ _3"></span><span class="ff4">1-2 <span class="_ _2"></span></span><span class="ls36">四种方法绘制双变量的一个函数的图形</span></div><div class="t m0 x18 hf y38 ffb fs7 fc2 sc0 ls36 ws0">2<span class="_ _1d"> </span><span class="ff9 fs2 fc0 ls0 ws9">M A<span class="_ _16"></span><span class="ls25 ws0">TLAB 5 <span class="ffc ls0">手册</span></span></span></div><div class="c x1 y1 w2 h2"><div class="t m0 xf h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">下载</div></div><div class="t m0 x19 hc y39 ff6 fs5 fc0 sc0 ls0 ws0">用<span class="ff4">surf</span>和<span class="ff4">shading interp</span>绘图<span class="_ _1e"> </span>用<span class="ff4">mesh</span>绘图</div><div class="t m0 x1a hc y3a ff6 fs5 fc0 sc0 ls0 ws0">用<span class="ff4">mesh<span class="_ _16"></span><span class="ff6">和隐藏线绘图</span></span></div><div class="t m0 x13 hc y3b ff6 fs5 fc0 sc0 ls0 ws0">用<span class="ff4">contour</span>绘图</div></div><div class="pi" data-data='{"ctm":[1.860465,0.000000,0.000000,1.860465,0.000000,0.000000]}'></div></div>

<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/bg3.jpg"><div class="t m0 x1b h5 y23 ff4 fs2 fc0 sc0 ls24 ws0">(c) MA<span class="_ _17"></span><span class="ls0 ws9">T L A B<span class="ff6 ls37 ws0">也能绘制一条参数曲线，例如：</span></span></div><div class="t m0 x1b h5 y3c ff9 fs2 fc0 sc0 ls37 ws0">x<span class="ff4">-<span class="_ _3"></span></span>y<span class="ff6 ls0">平面图如图<span class="_ _2"></span><span class="ff4 ws9">1 - 3<span class="_ _0"></span></span>所示。</span></div><div class="t m0 x1c he y3d ff6 fs6 fc1 sc0 ls0 ws0">图<span class="ff4">1-3 <span class="_ _7"> </span></span><span class="ls38">一个参数曲线图</span></div><div class="t m0 x1d h6 y3e ff5 fs2 fc0 sc0 ls0 ws0">■<span class="_ _5"> </span>例<span class="ff3 ls1c">1.2 <span class="_ _3"></span></span>函数分析</div><div class="t m0 x1b h5 y3f ff4 fs2 fc0 sc0 ls0 ws2">M AT L A B<span class="_ _3"></span><span class="ff6 ws0">命令<span class="_ _0"></span><span class="ff7 wsf">f z e r o<span class="_"> </span></span>和<span class="_ _3"></span><span class="ff7 wsf">f m i n<span class="_"> </span></span><span class="ls39">可以用于寻找一个函数的零点和最小值。</span></span></div><div class="t m0 x1b hd y40 ff6 fs2 fc0 sc0 ls0 ws0">函数<span class="_ _1f"> </span><span class="ls3a">可以用名叫<span class="_ _b"> </span></span><span class="ffa ws1b">f u n c<span class="_ _3"></span></span><span class="ls3b">的用户自定义函数<span class="_ _5"> </span><span class="ff4">(<span class="_ _0"></span></span></span>见<span class="_ _11"></span><span class="ff4 ws1b">2 . 9<span class="_"> </span></span>节<span class="_ _11"></span><span class="ff4">)<span class="_ _0"></span></span><span class="ls3c">表示，并存入一个名叫</span></div><div class="t m0 x1d hd y41 ffa fs2 fc0 sc0 ls0 ws9">f u n c . m<span class="_ _0"></span><span class="ff6 ws0">的<span class="_ _3"></span><span class="ff4">M<span class="_ _3"></span></span><span class="ls5">文件中。这个文件由下列行组成：</span></span></div><div class="t m0 x1b hd y42 ff6 fs2 fc0 sc0 ls0 ws0">如果这个<span class="_ _11"></span><span class="ff4">M<span class="_ _3"></span></span><span class="ls4">文件被存放在当前的工作目录中，或在一个称为<span class="_ _b"> </span></span><span class="ffa ws1c">m a t l a b<span class="_ _0"></span></span><span class="ls3d">的子目录中，函数<span class="_ _2"></span></span><span class="ffa ws1c">f u n c</span></div><div class="t m0 x1d h5 y43 ff6 fs2 fc0 sc0 ls3d ws0">就可以像预定义的<span class="_ _11"></span><span class="ff4 ls0 ws1d">M AT L A B<span class="_ _3"></span></span>函数一样调用。例如，调用<span class="_ _7"></span><span class="ff7 ls0 ws1e">x i s z e r o = f u n c ( 0 )<span class="_ _0"></span></span><span class="ls3e">，给出的答案是：</span></div><div class="t m0 x1b hb y44 ff8 fs5 fc0 sc0 ls3f ws0">xiszero =</div><div class="t m0 x1e ha y45 ffd fs5 fc0 sc0 ls0 ws0">－<span class="_ _3"></span><span class="ff8">1</span></div><div class="t m0 x1b h5 y46 ff6 fs2 fc0 sc0 ls40 ws0">用这样定义的函数，<span class="_ _7"></span><span class="ff4 ls0 ws1f">M AT L A B<span class="_ _3"></span></span><span class="ls29">提供了一个命令来寻找方程<span class="_ _b"> </span><span class="ff9 ls0 ws20">x e</span></span></div><div class="t m0 x1f h8 y47 ff9 fs4 fc0 sc0 ls0 ws20">x<span class="ff4">2</span></div><div class="t m0 x20 h6 y48 ff6 fs2 fc0 sc0 ls0 ws0">－</div><div class="t m0 x21 h9 y46 ff9 fs2 fc0 sc0 ls0 ws0">e</div><div class="t m0 x22 h8 y47 ff9 fs4 fc0 sc0 ls0 ws0">x<span class="ff4">2</span></div><div class="t m0 x23 h6 y48 ff6 fs2 fc0 sc0 ls0 ws0">－</div><div class="t m0 x24 h5 y46 ff4 fs2 fc0 sc0 ls0 ws20">s i n<span class="ff9">x</span></div><div class="t m0 x25 h8 y47 ff4 fs4 fc0 sc0 ls0 ws20">3</div><div class="t m0 x26 h5 y46 ff4 fs2 fc0 sc0 ls0 ws20">= 0<span class="_"> </span><span class="ff6 ls41 ws0">的零点。命令</span></div><div class="t m0 x1d h5 y49 ff7 fs2 fc0 sc0 ls0 wsf">x s o l v = f z e r o (<span class="_ _0"></span><span class="ff4 ws10">‘</span>f u n c<span class="_"> </span><span class="ff4 ws10">’<span class="_ _3"></span></span><span class="ws0">, 3)<span class="_ _7"></span><span class="ff6">给出：</span></span></div><div class="t m0 x1b hb y4a ff8 fs5 fc0 sc0 ls42 ws0">xsolv =</div><div class="t m0 x27 hb y4b ff8 fs5 fc0 sc0 ls0 ws12">1 . 2 1 9 4</div><div class="t m0 x1b h5 y4c ff6 fs2 fc0 sc0 ls13 ws0">在本例中，命令中的第<span class="_ _7"></span><span class="ff4">2<span class="_ _3"></span></span><span class="ls4">个自变量用的是<span class="_ _2"></span><span class="ff4">3</span><span class="ls5">，是开始计算的一个初始近似值。</span></span></div><div class="t m0 x1b h5 y4d ff6 fs2 fc0 sc0 ls0 ws0">如果在－<span class="_ _11"></span><span class="ff4">1<span class="_ _3"></span></span>≤<span class="_ _3"></span><span class="ff9">x<span class="_ _3"></span></span>≤<span class="_ _3"></span><span class="ff4 ws9">1 . 5<span class="_"> </span></span><span class="ls27">区间内绘制这个函数，则正确答案如图<span class="_ _b"> </span></span><span class="ff4 ws9">1 - 4<span class="_"> </span></span>所示。</div><div class="t m0 x28 he y4e ff6 fs6 fc1 sc0 ls0 ws0">图<span class="_ _3"></span><span class="ff4 ls24">1-4 </span>在－<span class="_ _0"></span><span class="ff4">1<span class="_ _3"></span></span>≤<span class="_ _3"></span><span class="ff9">x<span class="_ _3"></span></span>≤<span class="_ _3"></span><span class="ff4 ws21">1 . 5<span class="_ _0"></span></span><span class="ls43">区间内绘制函数<span class="_ _11"></span></span><span class="ff9">xe</span></div><div class="t m0 x29 h10 y4f ff9 fs8 fc1 sc0 ls0 ws0">x</div><div class="t m0 x2a h11 y50 ff4 fs9 fc1 sc0 ls0 ws0">2</div><div class="t m0 x2b h12 y4e ffe fs6 fc1 sc0 ls0 ws0">－<span class="ff9">e</span></div><div class="t m0 x2c h10 y4f ff9 fs8 fc1 sc0 ls0 ws0">x</div><div class="t m0 x2d h11 y50 ff4 fs9 fc1 sc0 ls0 ws0">2</div><div class="t m0 x2e he y4e ffe fs6 fc1 sc0 ls0 ws0">－<span class="ff4">sin<span class="ff9">x</span></span></div><div class="t m0 x2f h13 y4f ff4 fs8 fc1 sc0 ls0 ws0">3</div><div class="t m0 x30 h14 y51 ff6 fs6 fc1 sc0 ls0 ws0">的</div><div class="t m0 x31 h14 y4e ff6 fs6 fc1 sc0 ls0 ws0">图形</div><div class="c x32 y52 w3 h15"><div class="t m1 x33 h16 y53 ff9 fsa fc0 sc0 ls0 ws0">xe</div><div class="t m1 x34 h17 y54 ff9 fsb fc0 sc0 ls0 ws0">x</div><div class="t m1 x35 h18 y55 ff4 fsc fc0 sc0 ls0 ws0">2</div><div class="t m1 x2 h19 y56 fff fsa fc0 sc0 ls0 ws0">−<span class="_ _20"></span><span class="ff9">e</span></div><div class="t m1 x1d h17 y57 ff9 fsb fc0 sc0 ls0 ws0">x</div><div class="t m1 x36 h18 y58 ff4 fsc fc0 sc0 ls0 ws0">2</div><div class="t m1 x37 h19 y59 fff fsa fc0 sc0 ls0 ws0">−<span class="_ _20"></span><span class="ff4">sin<span class="_ _20"> </span><span class="ff9">x</span></span></div><div class="t m1 x38 h1a y5a ff4 fsb fc0 sc0 ls0 ws0">3</div></div><div class="t m0 x2e hf y38 ffc fs2 fc0 sc0 ls0 ws0">第<span class="_ _3"></span><span class="ff9">1<span class="_ _3"></span></span>章<span class="_ _21"> </span><span class="ff9 ws9">M AT L A B</span>是什么<span class="_ _22"> </span><span class="ffb fs7 fc2">3</span></div><div class="c x1 y1 w2 h2"><div class="t m0 x2 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">下载</div></div><div class="t m0 x39 h6 y5b ff5 fs2 fc0 sc0 ls0 ws0">■</div></div><div class="pi" data-data='{"ctm":[1.860465,0.000000,0.000000,1.860465,0.000000,0.000000]}'></div></div>

<div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/bg4.jpg"><div class="t m0 xb h5 y23 ff6 fs2 fc0 sc0 ls0 ws0">当<span class="_ _3"></span><span class="ff9">x<span class="_ _11"></span></span>在<span class="_ _0"></span><span class="ff4 ws22">0 . 5<span class="_ _11"></span></span>和<span class="_ _11"></span><span class="ff4">1<span class="_ _11"></span></span><span class="ls44">之间时，这个函数看起来有一个极小值，为正确找出这个极小值，用命令</span></div><div class="t m0 xa h5 y24 ff7 fs2 fc0 sc0 ls0 wsf">m p o i n t = f m i n (<span class="_"> </span><span class="ff4 ws10">‘<span class="_ _3"></span></span>f u n c<span class="_"> </span><span class="ff4 ws10">’<span class="_ _3"></span></span><span class="ls45 ws0">, 0.5, 1)<span class="_ _23"></span><span class="ff6 ls1">，其结果为：</span></span></div><div class="t m0 xb hb y5c ff8 fs5 fc0 sc0 ls46 ws0">mpoint =</div><div class="t m0 x3a hb y5d ff8 fs5 fc0 sc0 ls0 ws12">0 . 8 9 5 4</div><div class="t m0 xb h5 y5e ff6 fs2 fc0 sc0 ls0 ws0">用于检查<span class="_ _11"></span><span class="ff4 wsa">M AT L A B<span class="_"> </span></span><span class="lsd">中用户自定义函数的命令可参见第<span class="_ _b"> </span></span><span class="ff4 ws9">1 0</span>章和第<span class="_ _11"></span><span class="ff4">11<span class="_ _3"></span></span>章。</div><div class="t m0 x1d h6 y5f ff5 fs2 fc0 sc0 ls0 ws0">■<span class="_ _5"> </span>例<span class="_ _3"></span><span class="ff3 ls1c">1.3 <span class="_ _3"></span></span><span class="ls9">线性系统与特征值</span></div><div class="t m0 xb hd y60 ff4 fs2 fc0 sc0 ls24 ws0">(a) MA<span class="_ _17"></span><span class="ls0 ws9">T L A B<span class="ff6 ls47 ws0">可以用一个简单的命令行求解线性系统，系数矩阵<span class="_ _5"> </span><span class="ffa">A<span class="_ _4"></span><span class="ff6 ls0">和右侧<span class="_ _11"></span><span class="ffa">b<span class="_ _0"></span></span>定义如下：</span></span></span></span></div><div class="t m0 xb hd y61 ff6 fs2 fc0 sc0 ls9 ws0">这对应于线性系统<span class="_ _2"></span><span class="ffa ls0 ws9">A x = b<span class="_"> </span></span><span class="ls24">，如下所示：</span></div><div class="t m0 xa h6 y3e ff6 fs2 fc0 sc0 ls13 ws0">这可由如下命令求解：</div><div class="t m0 xb h1b y62 ff7 fs2 fc0 sc0 ls0 wsf">x = A \ b</div><div class="t m0 xa h6 y63 ff6 fs2 fc0 sc0 ls0 ws0">其结果为：</div><div class="t m0 xb h5 y64 ff4 fs2 fc0 sc0 ls0 ws0">(b) <span class="_ _0"></span><span class="ff6 ls48">还有许多矩阵控制命令。例如，例<span class="_ _12"> </span></span><span class="ws16">( a )</span><span class="ff6">中矩阵<span class="_ _11"></span></span>A<span class="ff6 ls49">的特征值很容易地可以由下列命令得到：</span></div><div class="t m0 x1d h6 y65 ff6 fs2 fc0 sc0 ls0 ws0">其给出：</div><div class="t m0 xb hd y66 ff6 fs2 fc0 sc0 ls0 ws0">矩阵<span class="_ _3"></span><span class="ffa ws23">E i g e n Ve c t o r s<span class="_ _3"></span></span>的列是<span class="_ _2"></span><span class="ffa">A<span class="_ _3"></span></span><span class="ls41">的特征向量，<span class="_ _2"></span></span><span class="ffa ws24">E i g e n Va l u e s</span><span class="ls4a">中对角线元素是特征值。由于矩阵<span class="_ _6"> </span><span class="ffa">A</span></span></div><div class="t m0 xa h6 y67 ff6 fs2 fc0 sc0 ls11 ws0">是对称的，因此，所有的特征值都是实数，三个特征向量是相互正交的。</div><div class="t m0 xb h5 y68 ff4 fs2 fc0 sc0 ls0 ws25">M AT L A B<span class="_ _0"></span><span class="ff6 ls4b ws0">中的基本概念是矩阵。基本的矩阵命令在第<span class="_ _a"> </span><span class="ff4">3</span><span class="ls4c">章描述，更多的命令将在第<span class="_ _6"> </span><span class="ff4">4</span><span class="ls0">、<span class="_ _0"></span><span class="ff4">7<span class="_ _3"></span></span>、</span></span></span></div><div class="t m0 xa h5 y69 ff4 fs2 fc0 sc0 ls0 ws0">8<span class="_ _3"></span><span class="ff6">、</span>9<span class="_ _3"></span><span class="ff6">章中描述。</span></div><div class="t m0 xa h6 y6a ff5 fs2 fc0 sc0 ls0 ws0">■<span class="_ _5"> </span>例<span class="_ _3"></span><span class="ff3 ls24">1.4 <span class="_ _3"></span></span><span class="ls4">曲线拟合与插值</span></div><div class="t m0 xb hd y6b ff4 fs2 fc0 sc0 ls0 ws0">(a) <span class="_ _b"> </span><span class="ff6 ls4">如果有两个向量<span class="_ _11"></span><span class="ffa">x<span class="_ _3"></span></span><span class="ls0">和<span class="_ _3"></span><span class="ffa">y<span class="_ _3"></span></span>表示的<span class="_ _11"></span><span class="ff9">x</span></span></span>-<span class="_ _0"></span><span class="ff9">y<span class="_ _3"></span><span class="ff6 ls4d">平面上的一组点，那么，可以对它们进行插值点或者拟</span></span></div><div class="t m0 xa h6 y6c ff6 fs2 fc0 sc0 ls4 ws0">合一条曲线。令</div><div class="t m0 x18 hf y38 ffb fs7 fc2 sc0 ls4 ws0">4<span class="_ _1d"> </span><span class="ff9 fs2 fc0 ls0 ws9">M A<span class="_ _16"></span><span class="ls38 ws0">TLAB 5 <span class="ffc ls0">手册</span></span></span></div><div class="c x1 y1 w2 h2"><div class="t m0 xf h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">下载</div></div><div class="t m0 x3b h6 y6d ff5 fs2 fc0 sc0 ls0 ws0">■</div><div class="t m0 x3b h6 y6e ff5 fs2 fc0 sc0 ls0 ws0">■</div></div><div class="pi" data-data='{"ctm":[1.860465,0.000000,0.000000,1.860465,0.000000,0.000000]}'></div></div>

<div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/62815ce23b39c07824f14c5c/bg5.jpg"><div class="t m0 x1b h5 y6f ff6 fs2 fc0 sc0 ls0 ws0">对应<span class="_ _11"></span><span class="ff9">x<span class="_ _0"></span><span class="ff4">-<span class="_ _0"></span></span>y<span class="_ _0"></span></span><span class="ls4c">平面上的<span class="_ _7"></span><span class="ff4">9<span class="_ _0"></span></span><span class="ls4e">个点。首先，展示以最小二乘法拟合数据的线性函数，这个可以通过</span></span></div><div class="t m0 x1d h5 y70 ff4 fs2 fc0 sc0 ls0 wsa">M AT L A B<span class="_"> </span><span class="ff6 lsa ws0">中的三个简单的命令来实现：</span></div><div class="t m0 x1b ha y3c ff7 fs5 fc0 sc0 ls4f ws0">p1=polyfit(x, y, 1)<span class="_ _24"> </span><span class="ls50">% p1=A<span class="_ _15"></span><span class="ff6 ls2a">向量等于一次多项式的系数。</span></span></div><div class="t m0 x1b ha y71 ff7 fs5 fc0 sc0 ls4f ws0">linc=polyval(p1, x)<span class="_ _24"> </span><span class="ls46">% linc=A<span class="_ _c"></span><span class="ff6 ls0">向量等于<span class="_ _11"></span><span class="ff7">x</span>点上多项式<span class="_ _2"></span><span class="ff7 ws12">p 1<span class="_"> </span></span>的值。</span></span></div><div class="t m0 x1b hc y27 ff7 fs5 fc0 sc0 ls51 ws0">plot(x, linc,x, y,<span class="_ _25"></span><span class="ff4 ls52">‘<span class="ff7 ls51">x<span class="_ _17"></span><span class="ff6 ls0">’<span class="_ _3"></span><span class="ff7">)<span class="_ _26"> </span>% <span class="_ _11"></span></span><span class="ls3e">绘制多项式和由‘<span class="_ _11"></span><span class="ff7 ls53">x</span><span class="ls25">’标记的数据。</span></span></span></span></span></div><div class="t m0 x1b h5 y5f ff6 fs2 fc0 sc0 ls0 ws0">结果见图<span class="_ _11"></span><span class="ff4 ws9">1 - 5 (</span>左图<span class="_ _0"></span><span class="ff4">)<span class="_ _0"></span></span>。</div><div class="t m0 x1b h5 y72 ff6 fs2 fc0 sc0 ls54 ws0">能以最小二乘法对一组点拟合高次多项式。对上面的命令行进行一点小改动就可以得到<span class="_ _27"> </span><span class="ff4">7</span></div><div class="t m0 x1d h6 y73 ff6 fs2 fc0 sc0 ls0 ws0">次多项式：</div><div class="t m0 x1b ha y74 ff7 fs5 fc0 sc0 ls55 ws0">p7=polyfit(x, y, 7); <span class="_ _1e"> </span><span class="ls50">% p7=A<span class="_ _15"></span><span class="ff6 ls0">向量等于<span class="_ _11"></span><span class="ff7">7<span class="_ _0"></span></span><span class="ls3e">次多项式的系数。</span></span></span></div><div class="t m0 x1b ha y75 ff7 fs5 fc0 sc0 ls0 ws12">x x = 1 : 0 . 2 5 : 8 ;<span class="_ _28"> </span><span class="ls56 ws0">% xx=<span class="_ _14"></span><span class="ff6 ls43">所有想要进行多项式计算的点。</span></span></div><div class="t m0 x1b ha y76 ff7 fs5 fc0 sc0 ls55 ws0">polc=polyval(p7, xx);<span class="_ _1e"> </span><span class="ls57">% polc=A<span class="_ _13"></span><span class="ff6 ls0">向量等于点<span class="_ _11"></span><span class="ff7 ws12">x x<span class="_"> </span></span>上多项式<span class="_ _11"></span><span class="ff7 ws12">p 7</span>的值。</span></span></div><div class="t m0 x1b ha y30 ff7 fs5 fc0 sc0 ls58 ws0">plot=(xx,polc, x, y,<span class="_ _29"></span><span class="ff6 ls0">’<span class="_ _3"></span><span class="ff7">x<span class="_ _3"></span></span>’<span class="_ _3"></span><span class="ff7">) <span class="_ _2a"> </span>% <span class="_ _0"></span></span><span class="ls3e">绘制多项式和由’<span class="_ _11"></span><span class="ff7 ls53">x<span class="_ _3"></span></span><span class="ls25">’标记的数据。</span></span></span></div><div class="t m0 x1b h5 y77 ff6 fs2 fc0 sc0 ls0 ws0">其结果如图<span class="_ _2"></span><span class="ff4 ws9">1 - 5 (</span>右图<span class="_ _0"></span><span class="ff4">)<span class="_ _0"></span></span>所示。</div><div class="t m0 x3c he y78 ff6 fs6 fc1 sc0 ls0 ws0">图<span class="ff4 ls24">1-5 <span class="_ _3"></span><span class="ff9">x</span>-<span class="ff9">y</span></span><span class="ls9">平面上对一组具有<span class="_ _2"></span><span class="ff4">9</span><span class="ls3d">个点的数据拟合的<span class="_ _2"></span><span class="ff4">1<span class="_ _3"></span></span></span></span>次和<span class="_ _3"></span><span class="ff4">7<span class="_ _3"></span></span>次多项式</div><div class="t m0 x1b h5 y79 ff4 fs2 fc0 sc0 ls59 ws0">(b) MA<span class="_ _17"></span><span class="ls0 ws26">T L A B<span class="ff6 ls27 ws0">提供了二维和三维的内插函数。给定一组点<span class="_ _6"> </span><span class="ff4">(<span class="ff9">x</span></span></span></span></div><div class="t m0 x3d h1c y7a ff9 fs4 fc0 sc0 ls27 ws0">i</div><div class="t m0 x3e h9 y79 ff6 fs2 fc0 sc0 ls0 ws0">，<span class="_ _3"></span><span class="ff9">y</span></div><div class="t m0 x3f h1c y7a ff9 fs4 fc0 sc0 ls0 ws0">i</div><div class="t m0 x40 h5 y79 ff4 fs2 fc0 sc0 ls0 ws0">)<span class="_ _3"></span><span class="ff6 ls1">和一些内插点<span class="_ _11"></span><span class="ff4">x<span class="_ _14"></span><span class="ff9">˜</span></span></span></div><div class="t m0 x41 h1c y7b ff9 fs4 fc0 sc0 ls1 ws0">i</div><div class="t m0 x42 h5 y79 ff6 fs2 fc0 sc0 ls1 ws0">,<span class="ff4 ls0 ws27">M AT L A B</span></div><div class="t m0 x1d h6 y7c ff6 fs2 fc0 sc0 ls20 ws0">能返回通过对这些数据内插的插入点的值，这可以有不同的方法实现。作为一个例子，将使</div><div class="t m0 x1d h5 y7d ff6 fs2 fc0 sc0 ls0 ws0">用<span class="ff4 ws16">( a )<span class="_ _3"></span></span><span class="ls5a">中的一组点来给出在下列点中插入的值：</span></div><div class="t m0 x43 he y7e ff6 fs6 fc1 sc0 ls0 ws0">图<span class="_ _3"></span><span class="ff4 ls14">1-6 piecewise </span>线性函数插值<span class="_ _7"> </span><span class="ff4">(<span class="_ _3"></span></span>左<span class="_ _3"></span><span class="ff4">)<span class="_ _3"></span></span><span class="ls43">和三次样条插值<span class="_ _2"></span><span class="ff4">(<span class="_ _3"></span></span></span>右<span class="_ _3"></span><span class="ff4">)</span></div><div class="t m0 x2e hf y38 ffc fs2 fc0 sc0 ls0 ws0">第<span class="_ _3"></span><span class="ff9">1<span class="_ _3"></span></span>章<span class="_ _21"> </span><span class="ff9 ws28">M AT L A B</span>是什么<span class="_ _1d"> </span><span class="ffb fs7 fc2">5</span></div><div class="c x1 y1 w2 h2"><div class="t m0 x2 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">下载</div></div><div class="t m0 x44 ha y7f ff6 fs5 fc0 sc0 ls0 ws0">线性插值</div><div class="t m0 x45 ha y80 ff6 fs5 fc0 sc0 ls0 ws0">三次样条插值</div></div><div class="pi" data-data='{"ctm":[1.860465,0.000000,0.000000,1.860465,0.000000,0.000000]}'></div></div>