Tabular and centering error

Question

I want to create a tabular with fixed column width and centered text. I write it like that:

\begin{table}[ht]
\begin{center}
\begin{tabular}{p{4cm}p{4cm}p{4cm}}
\hline
\multicolumn{3}{c}{\textbf{High resolution model}} \\
\hline
\centering $\alpha_{H,1}$ & \centering $\alpha_{H,2}$ & \centering $\alpha_{H,3}$  \\
 bla & bla & bla \\
\end{tabular}
\end{center}
\end{table}

I use the centering command because when using "p{4cm}p{4cm}p{4cm}" to fix the size of the columns, by default the text is aligned on the left. But when I want to compile I get the following error : "! Extra alignment tab has been changed to \cr." that I do not understand and that I am not able to solve.

Any help would be appreciated :)

Answer 1

I would like to suggest that you (a) load the array package and (b) use this package's \newcolumntype directive to create a centered version of the basic p column type:

\newcolumntype{C}[1]{>{\centering\arraybackslash}p{#1}}

Then, replace

\begin{tabular}{p{4cm}p{4cm}p{4cm}}

with

\begin{tabular}{C{4cm}C{4cm}C{4cm}}

and you're all set.

---

A full MWE (minimum working example):

\documentclass{article}
\usepackage{array} % for "\newcolumtype" macro
\newcolumntype{C}[1]{>{\centering\arraybackslash}p{#1}}
\begin{document}
\begin{table}[ht]
\centering
\begin{tabular}{*{3}{C{4cm}}}
\hline
\multicolumn{3}{c}{\textbf{High resolution model}} \\
\hline
$\alpha_{H,1}$ & $\alpha_{H,2}$ & $\alpha_{H,3}$  \\
bla & bla & bla \\
\hline
\end{tabular}
\end{table}
\end{document}