# How to edit table automatic width?

How do I make the width not too big and how do I make the matrix appear at the center ? I copied this format from somewhere but i don't know how to edit it.

\begin{center}
\begin{table}[h]
\begin{tabu} to 1\textwidth {| X[c,m] | X[c,m] | X[c,m] | X[c,m] |@{}m{0pt}@{}}
\hline
k & $\pi$ & $\bm{\mu}$ & $\bm{S}$ \\ \hline
1 & 0.865
& [1.54   1.63    3.88]
& $\begin{bmatrix} .0187 & .0043 & .0101 \\ .0043 & .0104 & .0152 \\ .0101 & .0152 & .1814 \end{bmatrix}$ \\[5ex] \hline
2 & 0.135
& [1.76   0.66    0.84]
& $\begin{bmatrix} .0187 & .0043 & .0101 \\ .0043 & .0104 & .0152 \\ .0101 & .0152 & .1814 \end{bmatrix}$ \\[5ex] \hline
\end{tabu}
\caption{Maximum Likelihood Estimates of the component parameters.}
\label{estimatedparameters}
\end{table}
\end{center}


• Do you have special reason to use tabu package for table? – Zarko Oct 14 '16 at 5:33
• Off-topic: Don't embed a table environment inside a center environment. If the tabular material inside the table needs to be centered, provide a \centering instruction immediately after \begin{table}. – Mico Oct 14 '16 at 7:51

If you persist to use tabu, than try the following:

\documentclass{article}
\usepackage{tabu}
\usepackage{bm,mathtools}

\begin{document}
\begin{table}[htb]
\tabulinesep =_3pt^3pt
\begin{tabu} to \textwidth {| X[1,c,m] | X[1,c,m] | X[2,c,m] | X[3,c,m,]|}
\hline
k   & $\pi$ & $\bm{\mu}$        & \bm{S}            \\
\hline
1   & 0.865 & [1.54 1.63 3.88]  & \begin{bmatrix}
.0187 & .0043 & .0101 \\
.0043 & .0104 & .0152 \\
.0101 & .0152 & .1814 \end{bmatrix}     \\
\hline
2   & 0.135 & [1.76 0.66 0.84]  & \begin{bmatrix}
.0187 & .0043 & .0101 \\
.0043 & .0104 & .0152 \\
.0101 & .0152 & .1814 \end{bmatrix}     \\
\hline
\end{tabu}
\caption{Maximum Likelihood Estimates of the component parameters.}
\label{estimatedparameters}
\end{table}
\end{document}


It gives:

Replace

\begin{tabu} to 1\textwidth {| X[c,m] | X[c,m] | X[c,m] | X[c,m] |@{}m{0pt}@{}}


with

\begin{tabu}{|c|c|c|c|}


This will centre-align all of the table contents, without spacing them out, and make sure the matrices fit into the last column.