3

When I try to remove the outer brackets in the following diagram, by removing the first occurrence of \begin{pmatrix} and the last occurrence of \end{pmatrix} I get the error misplaced alignment tab character &. I cannot see which tab character is causing the problem and why it is causing the problem. How can I remove the outer parentheses without incurring this problem, and preserving all other properties as is, except for perhaps making the gap between rows slightly smaller. I have used \\ \\ below, but this gap is too big, whilst \\ is too small.

\documentclass[11pt]{beamer}
\usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}
\usepackage{subfig}
\usetheme{Madrid} 
\usepackage{empheq}
\usepackage{multicol}
\usepackage{gb4e}

\begin{document}

\begin{frame}

\[\begin{pmatrix}\begin{matrix} \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array} \\ \\ \text{John} \\ \\ \cfrac{\ \operatorname{[\;]}\ }{\ saw\ } \end{matrix} &
\begin{pmatrix}
\begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}     & \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}  \\  \\ 
\text{saw}         & \text{Mary}\\ \\
\cfrac{\ \operatorname{[\;]}\ }{\ a\ } & \cfrac{\ \operatorname{[\;]}\ }{\ b\ }
\end{pmatrix}
\end{pmatrix}
\]


\end{frame}

\end{document}
4

Change pmatrix (which automatically add a pair of brackets) to matrix:

\documentclass[11pt]{beamer}
\usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}
\usepackage{subfig}
\usetheme{Madrid} 
\usepackage{empheq}
\usepackage{multicol}
\usepackage{gb4e}

\begin{document}

\begin{frame}

\[\begin{matrix}\begin{matrix} \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array} \\ \\ \text{John} \\ \\ \cfrac{\ \operatorname{[\;]}\ }{\ saw\ } \end{matrix} &
\begin{pmatrix}
\begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}     & \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}  \\  \\ 
\text{saw}         & \text{Mary}\\ \\
\cfrac{\ \operatorname{[\;]}\ }{\ a\ } & \cfrac{\ \operatorname{[\;]}\ }{\ b\ }
\end{pmatrix}
\end{matrix}
\]


\end{frame}

\end{document}

enter image description here

Avoid using double \\s. You always have \\[]:

\documentclass[11pt]{beamer}
\usepackage{pgfpages,amsmath,amssymb,mathtools,color, graphicx, amsfonts, braket}
\usepackage{subfig}
\usetheme{Madrid} 
\usepackage{empheq}
\usepackage{multicol}
\usepackage{gb4e}

\begin{document}

\begin{frame}

\[\begin{matrix}\begin{matrix} \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array} \\[2ex] \text{John} \\ \cfrac{\ \operatorname{[\;]}\ }{\ saw\ } \end{matrix} &
\begin{pmatrix}
\begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}     & \begin{array}{c|c}
\multicolumn{2}{c}{\cfrac{\ t \ }{\ e \to e \to t \ }}
\end{array}  \\[2ex] 
\text{saw}         & \text{Mary}\\
\cfrac{\ \operatorname{[\;]}\ }{\ a\ } & \cfrac{\ \operatorname{[\;]}\ }{\ b\ }
\end{pmatrix}
\end{matrix}
\]


\end{frame}

\end{document}

enter image description here

| improve this answer | |
  • Brilliant. The other thing I wanted to know was how to get the space between each row slightly less. I had \` before and in the above it is \\ \`. But this is slightly too big, whilst `\` is too small. – user65526 Apr 12 '19 at 14:01
  • I have edited my question slightly to incorporate this. – user65526 Apr 12 '19 at 14:04
  • I've tried that but it doesn't produce enough space between the top two rows. Can I use 0.5ex? – user65526 Apr 12 '19 at 14:07
  • @user65526 Look at my edited answer. I used the default spacing in the space between row 2 and row 3, but \\[2ex] between row 1 and row 2. In fact, you can add anything between [ and ], for example \\[1cm], even negative numbers can be added. – user156344 Apr 12 '19 at 14:08
  • @user65526 Do you have any questions? – user156344 Apr 12 '19 at 14:19

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