[Tex/LaTex] Missing number, treated as zero. *

errorsmultirowtables

I'm having the worst time ever figuring how to get rid of this error I'm getting!

\documentclass[12pt, onecolumn]{article}
\usepackage{multicol, multirow, array}
\usepackage{calc}
\usepackage{colortbl}
\usepackage{geometry}
\usepackage{enumitem}
\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{fancyhdr}
\usepackage{graphicx}
\usepackage{arydshln}
\usepackage{booktabs}
\usepackage{bigstrut}        

\begin{document}
\begin{center}
\begin{tabular}{|ccc|cc|c|c|}
\hline
\multicolumn{3}{c}{\multirow{2}{*}{$A$}} & \multicolumn{2}{c}{\multirow{2}{*}{$I_m$}} & $_m{\hat{0}}$ & $\hat{b}$\\ 
\hline
\multicolumn{3}{c}{$\bar{c}$} & \multicolumn{2}{*}{$\bar{0}_m$} & 1 & $d$\\ 
\hline
\multicolumn{3}{c}{$\bar{0}_n$}&\multicolumn{2}{*}{$\bar{0}_m$}&0&$0$\\ 
\hline
\end{tabular}
\end{center} 
\end{document}

The table should look like this:

enter image description here

Best Answer

The {*} is used as the second argument of multirow to denote the natural width of its contents. For \multicolumn, the second argument is the column type of the multicolumn.

I would suggest using two centred fixed width columns for the first two, \bigstrut to set the height of the first row, and cellspace to add some minimal vertical padding to the other row:

  \documentclass[12pt, onecolumn]{article}
    \usepackage{multicol, multirow, array}
    \usepackage{calc}
    \usepackage{colortbl}
    \usepackage{geometry}
    \usepackage{enumitem}
    \usepackage{mathtools}
     \usepackage{fancyhdr}
     \usepackage{graphicx}
    \usepackage{arydshln}
    \usepackage{booktabs, cellspace}
    \setlength{\cellspacetoplimit}{5pt}
    \setlength{\cellspacebottomlimit}{4pt}
    \usepackage{bigstrut}

\begin{document}

 \begin{center}

 \setlength{\bigstrutjot}{3ex}
    \begin{tabular}{|>{\centering}p{1.8cm}|S{>{\centering}p{1.2cm}}:c|c|}
    \hline
   \bigstrut$A$ & $I_m$ & ${_m{}\hat{0}}$ & $\hat{b}$\\
    \hdashline
      $\bar{c}$ & $\bar{0}_m$ & 1 & $d$\\
    \hline
    $\bar{0}_n$ & $\bar{0}_m$ &0&$0$\\
    \hline
    \end{tabular}
    \end{center}

\end{document}

enter image description here

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