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I'm trying to use the tickz package in beamer, but the bug is appearing

Missing \endcsname inserted

The code of the diagram I'm drawing is

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage{utopia}
\usepackage{tikz}
\usetikzlibrary{shadows}
\usetikzlibrary{arrows,shapes}

\usetheme{Madrid}
\usecolortheme{default}

\begin{document}

\begin{frame}
\begin{equation*}
\begin{tikzpicture}
\matrix (m) [matrix of math nodes,row sep=3em,column sep=4em,minimum     width=2em]
{
 K_0(I) & K_0(A) & K_0(B) \\
 K_1(B) & K_1(A) & K_1(I) \\};
\path[-stealth]
(m-2-1) edge node [left] {$\delta_1$} (m-1-1)
(m-1-1) edge node [above] {$K_0(\varphi)$} (m-1-2)
(m-1-2) edge node [above] {$K_0(\psi)$} (m-1-3)
(m-2-3) edge node [below] {$K_1(\varphi)$} (m-2-2)
(m-2-2) edge node [below] {$K_1(\psi)$} (m-2-1);
\end{tikzpicture}
\end{equation*}
\end{frame}
\end{document}

If I try this same code into a normal document (without the beamer) it works normally

Lucas Sá
  • 13
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    Welcome to TeX-SE! You need to use ampersand replacement and to load the matrix library. \matrix (m) [ampersand replacement =\&,matrix of math nodes,row sep=3em,column sep=4em,minimum width=2em] { K_0(I) \& K_0(A) \& K_0(B) \\ K_1(B) \& K_1(A) \& K_1(I) \\}; and \usetikzlibrary{matrix} in the preamble. –  Apr 17 '19 at 18:37
  • To understand why marmot's answer works, you can have a look at the answer to https://tex.stackexchange.com/questions/208408/tikz-matrix-undefined-control-sequence – sztruks Apr 17 '19 at 18:43

1 Answers1

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just ad fragile option to \begin{frame} and in preamble missed library matrix. i also suggest to slightly change your matrix's code by using quotes library for edge labels:

\documentclass{beamer}
\usetheme{Madrid}
\usecolortheme{default}
%\usepackage[utf8]{inputenc}  % it is used by default, as i remember
\usepackage{utopia}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,
                matrix,
                quotes,
                shapes}

\begin{document}
\begin{frame}[fragile]  % <---
    \begin{center}
\begin{tikzpicture}[auto=left]
\matrix (m) [matrix of math nodes,
             row sep=3em, column sep=5em,
             ]
{
 K_0(I) & K_0(A) & K_0(B) \\
 K_1(B) & K_1(A) & K_1(I) \\
 };
\path[-Stealth]
    (m-2-1) edge["$\delta_1$"]      (m-1-1)
    (m-1-1) edge["$K_0(\varphi)$"]  (m-1-2)
    (m-1-2) edge["$K_0(\psi)$"]     (m-1-3)
    (m-2-3) edge["$K_1(\varphi)$"]  (m-2-2)
    (m-2-2) edge["$K_1(\psi)$"]     (m-2-1);
\end{tikzpicture}
    \end{center}
\end{frame}
\end{document}

enter image description here

addendum:

above solution can be write much shorter with use of the tikz-cd package:

\documentclass{beamer}
\usetheme{Madrid}
\usecolortheme{default}
%\usepackage[utf8]{inputenc}  % it is used by default, as i remember
\usepackage{utopia}
\usepackage{tikz-cd}

\begin{document}
\begin{frame}[fragile]
    \begin{center}
\begin{tikzcd}[row sep=3em, column sep=5em]
 K_0(I) \ar[r,"K_0(\varphi)"]
        & K_0(A) \ar[r,"K_0(\psi)"]
                & K_0(B)                            \\
 K_1(B) \ar[u,"\delta_1"]
        & K_1(A) \ar[l,"K_0(\psi)"]
                & K_1(I) \ar[l,"K_0(\varphi)"]    \\
\end{tikzcd}
    \end{center}
\end{frame}
\end{document}

rezultat is the same as before (since tikz-cd is based on matrix library).

Zarko
  • 296,517