<span class="hljs-comment">//4. 对角矩阵</span>
<span class="hljs-comment">//4.1 构造对角矩阵</span>
<span class="hljs-function">Eigen::VectorXd <span class="hljs-title">vector</span><span class="hljs-params">(<span class="hljs-number">5</span>)</span></span>;                <span class="hljs-comment">//构建5维向量</span>
vector&lt;&lt;<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">4</span>,<span class="hljs-number">5</span>;                        <span class="hljs-comment">//向量赋值</span>
<span class="hljs-function">Eigen::MatrixXd  <span class="hljs-title">C</span><span class="hljs-params">(vector.asDiagonal())</span></span>;  <span class="hljs-comment">//使用向量生成对角阵</span>
std::cout &lt;&lt; <span class="hljs-string">&quot;\nC= \n&quot;</span> &lt;&lt; C &lt;&lt; std::endl;