底部支撑重叠文本

Question

我正在尝试输入下图中的公式。括号上的文字很长，无法换行。你能帮我解决这个问题吗？谢谢。

方程：

  \documentclass{article}
  \usepackage{underoverlap}
  \begin{document}

  $Q_{t+1}(s_t,a_t)= \UOLunderbrace{Q_{t}(s_t,a_t)}_{old\ value}  + 
  \UOLunderbrace{\alpha_{t}(s_t,a_t)}_{learning\ rate}
  \bigg(
      \UOLoverbrace{
         \UOLunderbrace{R_{t+1}}_{reward}+
         \UOLunderbrace{\gamma}_{discount\ factor}
         \UOLunderbrace{max Q_{t}(s_t,a)}_{optimal\ future\ value}
      }^{learned\ value}-
      \UOLunderbrace{Q_{t}(s_t,a_t)}_{old\ value}
  \bigg)$
  \end{document}

Answer 1

您不想使用underoverlap，因为这样不会留下必要的空间；您可以使用\substack，但在这种情况下，我更喜欢“手动”完成。

\documentclass{article}
\usepackage{amsmath}

\newcommand{\xsub}[1]{%
  \mbox{\scriptsize\begin{tabular}{@{}c@{}}#1\end{tabular}}%
}

\begin{document}

$Q_{t+1}(s_t,a_t)= \underbrace{Q_{t}(s_t,a_t)}_{\xsub{old value}}  +
  \underbrace{\alpha_{t}(s_t,a_t)}_{\xsub{learning rate}}
  \bigg(
      \overbrace{
         \underbrace{R_{t+1}}_{\xsub{reward}}+
         \underbrace{\gamma}_{\xsub{discount\\factor}}
         \underbrace{\max Q_{t}(s_t,a)}_{\xsub{optimal\\future value}}
      }^{\xsub{learned value}}-
      \underbrace{Q_{t}(s_t,a_t)}_{\xsub{old value}}
  \bigg)$

\end{document}