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<title> 基本矩阵运算元 </title>
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<font COLOR="#0000FF">

<h1>5.1.1 基本矩阵运算元</h1>
</font>

<hr>

<p>我们在第二章已说明过 MATLAB 的运算是以阵列(array)及矩阵 <font FACE="Times New Roman">(matrix) </font>方式在做运算,而这二者在MATLAB的 
基本运算性质不同,阵列强调元素对元素的运算,而矩阵则采用线性代数的运算方式。我们就来说明矩阵运算 
的特点。 <br>
</p>

<p>以下将阵列及矩阵的运算符号及其意义列出 </p>

<table BORDER="1">
  <tr>
    <td WIDTH="106">阵列运算符号</td>
    <td WIDTH="104">矩阵运算符号 </td>
    <td WIDTH="72">功能</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">+</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">+</font> </td>
    <td WIDTH="72">加</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">-</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">-</font> </td>
    <td WIDTH="72">减</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">.*</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">*</font> </td>
    <td WIDTH="72">乘</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">./</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">/</font> </td>
    <td WIDTH="72">左除</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">.\</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000">\</font> </td>
    <td WIDTH="72">右除</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">.^</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">^</font> </td>
    <td WIDTH="72">次方</td>
  </tr>
  <tr>
    <td WIDTH="106"><p align="center"><font COLOR="#FF0000" FACE="Times New Roman">.</font><font COLOR="#FF0000">'</font> </td>
    <td WIDTH="104"><p align="center"><font COLOR="#FF0000">'</font> </td>
    <td WIDTH="72">转置</td>
  </tr>
</table>

<p>利用这些运算符号即可进行以下的矩阵运算。 </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A=[2 5 1; 7 3 8; 4 5 21; 16 13 
0];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A' % A</font><font COLOR="#FF0000">的转置矩阵</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">A =</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">2 7 4 16</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">5 3 5 13</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">1 8 21 0<br>
</font></p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A=[4 -1 3]; B=[-2 5 2];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; dot_prod = sum(A.*B) % </font><font COLOR="#FF0000">二个阵列做内积</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">dot_prod =</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">-7</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; c=dot(A,B) % </font><font COLOR="#FF0000">以</font><font COLOR="#FF0000" FACE="Times New Roman">dot</font><font COLOR="#FF0000">函数也可做内积运算</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">c =</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">-7<br>
</font></p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A=[4; -1; 3];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; dot_prod = sum(A'.*B); % </font><font COLOR="#FF0000">如果</font><font COLOR="#FF0000" FACE="Times New Roman">A</font><font COLOR="#FF0000">是行阵列则先做转置,再做内积 <br>
</font></p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; F=[2 5 -1]; G=[0 1 -3];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; out_prod=F'*G; % </font><font COLOR="#FF0000">二矩阵做外积<br>
</font></p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A=[2,5,1; 0,3,-1];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; B=[1,0,2; -1,4,-2; 5,2,1];</font> 
</p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; C=A*B % </font><font COLOR="#FF0000">矩阵相乘,注意二个矩阵的大小须相容</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">C =</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">2 22 -5</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">-8 10 -7<br>
</font></p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A=[2 1; 4 3];</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">&gt;&gt; A^2 % </font><font COLOR="#FF0000">矩阵次方</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">ans =</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">4 1</font> </p>

<p><font COLOR="#FF0000" FACE="Times New Roman">16 9<br>
</font></p>

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