[Tex/LaTex] Undefined control sequence error \end{gather}

alignequationserrors

\documentclass{article}
\usepackage{mathtools,amssymb}

\begin{document}

\begin{gather}    
\begin{split}

(1-\underset{(0.034)}{0.060}{\textit{B}}^{12}-\underset{(0.032)}{0.123}{\textit{B}}^{2(12)}){y}_t &=(1-\underset{(0.016)}{0.878}\textit{B}^{12})(1-\underset{(0.012)}{0.969}\textit{B}){e}_t\\ 

\end{split}

\notag\\

Box-Ljung \quad test \quad for\quad residuals\quad {\chi}^2= 15.151 \quad df= 12 \quad p-value = 0.233 \notag\\

\CENTERLINE {(Standard\quad errors\quad in\quad parentheses)}\notag

\end{gather} 

\end{document}

Best Answer

Don't use blank lines in math mode, post a complete MWE, and please don't tell me that Box-Ljung is still being taught......

\documentclass{article}
\usepackage{mathtools,amssymb}

\begin{document}

\begin{gather}    
\begin{split}
(1-\underset{(0.034)}{0.060}{\textit{B}}^{12}-\underset{(0.032)}{0.123}{\textit{B}}^{2(12)}){y}_t &=(1-\underset{(0.016)}{0.878}\textit{B}^{12})(1-\underset{(0.012)}{0.969}\textit{B}){e}_t\\ 
\end{split}
\notag\\
\text{Box-Ljung \quad test \quad for\quad residuals}\quad {\chi}^2= 15.151 \quad df= 12 \quad p-value = 0.233 \notag\\
%\CENTERLINE 
{\text{(Standard errors in parentheses)}}\notag
\end{gather} 

\end{document}
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