How to put table in full page when Document format is double column

Question

I have a Latex document with the elsarticle document class (Elsevier Journal) which is in double column. I'm trying to fit a long table into a single column, but it doesn't work, the table is messy and doesn't take up the full width. I've tried adding a * to the longtable command, but that doesn't work either.

UPDATE: I also tried the command \onecolumn after begin{longtable} and the command \doublecolumn at the end, but it didn't work, the full paper becomes one column, which I don't want.

An extract of my table with sample data (but with far fewer rows) is below :

\documentclass[5p,times,twocolumn,authoryear]{elsarticle}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{placeins}
\usepackage{multirow}
\usepackage{afterpage}
\usepackage{xcolor}
\usepackage{longtable}

\begin{document}

\afterpage{%
\begingroup
\scriptsize
\centering
\begin{longtable} [c]{p{1cm}p{1.8cm}p{1cm}p{2cm}p{2.1cm}p{1.3cm}p{2cm}}
\caption{High Level Overview of Existing Frameworks}
\label{tab:general-description-v1}\\
\hline
%\rowcolor[HTML]{9B9B9B} 
\textbf{Name} &
\textbf{Authors} &
\textbf{Year} &
\textbf{Column A} &
 \textbf{Column B} & 
\textbf{Column C} &
  \textbf{Column D} \\ \hline
\endfirsthead
%
\multicolumn{6}{c}%
{{\bfseries Table \thetable\ continued from previous page}} \\
\hline
%\rowcolor[HTML]{9B9B9B} 
\textbf{Name} &
\textbf{Authors} &
\textbf{Year} &
 \textbf{Column A} &
 \textbf{Column B} &
 \textbf{Column C} &
\textbf{Column D} \\ \hline
\endhead
%

AA\textsuperscript{*}&
citation 1 &
2019 - 2020 &
data 1 &
data 2 &
\begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
\begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \hline

  
\multirow{2}{*}{BB\textsuperscript{*} }
&citation 2 &
  2010 &
  \begin{tabular}[c]{@{}l@{}}data 1 \end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 2\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \cline{2-7}

&citation 3 &
  2013 &
  data 1 &
  \begin{tabular}[c]{@{}l@{}}data 2\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \hline

\end{longtable}
\endgroup
}%
\raggedbottom

\end{document}

Any ideas how to fix this?

Answer 1

Switch to oncolumn mode before you start the longtable:

\documentclass[5p,times,twocolumn,authoryear]{elsarticle}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{placeins}
\usepackage{multirow}
\usepackage{afterpage}
\usepackage{xcolor}
\usepackage{longtable}
\usepackage{lipsum}

\begin{document}

\lipsum

\afterpage{%
\begingroup
\onecolumn
\scriptsize
\centering
\begin{longtable} [c]{p{1cm}p{1.8cm}p{1cm}p{2cm}p{2.1cm}p{1.3cm}p{2cm}}
\caption{High Level Overview of Existing Frameworks}
\label{tab:general-description-v1}\\
\hline
%\rowcolor[HTML]{9B9B9B} 
\textbf{Name} &
\textbf{Authors} &
\textbf{Year} &
\textbf{Column A} &
 \textbf{Column B} & 
\textbf{Column C} &
  \textbf{Column D} \\ \hline
\endfirsthead
%
\multicolumn{6}{c}%
{{\bfseries Table \thetable\ continued from previous page}} \\
\hline
%\rowcolor[HTML]{9B9B9B} 
\textbf{Name} &
\textbf{Authors} &
\textbf{Year} &
 \textbf{Column A} &
 \textbf{Column B} &
 \textbf{Column C} &
\textbf{Column D} \\ \hline
\endhead
%

AA\textsuperscript{*}&
citation 1 &
2019 - 2020 &
data 1 &
data 2 &
\begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
\begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \hline

  
\multirow{2}{*}{BB\textsuperscript{*} }
&citation 2 &
  2010 &
  \begin{tabular}[c]{@{}l@{}}data 1 \end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 2\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \cline{2-7}

&citation 3 &
  2013 &
  data 1 &
  \begin{tabular}[c]{@{}l@{}}data 2\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 3\end{tabular} &
  \begin{tabular}[c]{@{}l@{}}data 4\end{tabular} \\ \hline

\end{longtable}
\twocolumn
\endgroup
}%
\raggedbottom

\lipsum

\end{document}