我怎样才能让东西在 align* 内居中

Question

我的代码是这样的：

\begin{center}
    \begin{align*}
    & \min_{w,b,\xi,\xi'}\ \ \ \ \frac{1}{2}\boldsymbol{w}^T\boldsymbol{w} + C\sum_{i=1}^l (\xi_i + \xi'_i) \\
    & subject\ to \\
    & \boldsymbol{w}^t\phi(\boldsymbol{x_i}) + b - y_i \leq \epsilon + \xi_i \\
    & y_i - \boldsymbol{w}^T\phi(\boldsymbol{x_i}) - b \leq \epsilon + \xi'_i \\
    & \xi_i, \xi'_i \geq 0,\ \ i = 1,\dots, l \\
    \end{align*}
\end{center}

并产生以下输出：

我希望“受制于”下的内容居中，位于第一行下方，而不是左对齐。我尝试将它们放在\begin{center}...内，\end{center}但它给了我很多错误

Answer 1

使用聚集

\documentclass{article}
\usepackage{amsmath}

\usepackage{showframe} % just for the example

\begin{document}

\begin{gather*}
   % \begin{align}
    \min_{w,b,\xi,\xi'}\ \ \ \ \frac{1}{2}\boldsymbol{w}^T\boldsymbol{w} + 
    C\sum_{i=1}^l (\xi_i + \xi'_i) \\
    subject\ to \\
    \boldsymbol{w}^t\phi(\boldsymbol{x_i}) + b - y_i \leq \epsilon + \xi_i \\
    y_i - \boldsymbol{w}^T\phi(\boldsymbol{x_i}) - b \leq \epsilon + \xi'_i \\
    \xi_i, \xi'_i \geq 0,\ \ i = 1,\dots, l 
    % \end{align}
    \end{gather*}

\end{document}

Answer 2

我建议使用专用包进行布局，optidef::

\documentclass{article}
\usepackage{optidef}

\begin{document}

\begin{mini*}|s|
 {w,b,\xi,\xi'}{\frac{1}{2}\boldsymbol{w}^T\boldsymbol{w} + C\sum_{i=1}^l (\xi_i + \xi'_i)}
 {}{}
 \addConstraint{\boldsymbol{w}^t\phi(\boldsymbol{x_i}) + b - y_i}{\leq \epsilon + \xi_i}
 \addConstraint{y_i - \boldsymbol{w}^T\phi(\boldsymbol{x_i}) - b}{\leq \epsilon + \xi’_i}
 \addConstraint{ \xi_i, \xi'_i}{\geq 0,}{\quad i = 1,\dots, l}
\end{mini*}

\end{document}