Add caption after tabular and adjust table alignment

Question

I want to add a caption below my table and my table is too aligned to the right, I want to bring it more to the left.

Here is the code of my table:

\documentclass[a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{array,booktabs}

% added packages and column definitions
\usepackage{ragged2e}           % for smart align of cells' content
    \usepackage{enumitem}       % for nice list
\newlist{tabitemize}{itemize}{1}% <-- defined new list
\setlist[tabitemize]{nosep,     % <-- new list setup
                     topsep     = 0pt       ,
                     partopsep  = 0pt       ,
                     leftmargin = *         ,
                     label      = $\bullet$ ,
                     before     = \vspace{-0.6\baselineskip},
                     after      = \vspace{-\baselineskip}
                     }
\newcolumntype{I}[1]{>{\RaggedRight\arraybackslash             % <-- for lists in columns
                    \tabitemize} p{#1}<{\endtabitemize}}
\newcommand\mch[1]{\multicolumn{1}{c}{\small{#1}}}  % <-- for columns headers  

\begin{document}
\newcommand*{\tstack}[1]{%
  \begingroup
    \renewcommand*{\arraystretch}{1}%
    \begin{tabular}[t]{@{}l@{}}#1\end{tabular}%
  \endgroup
}
\xdef\BaseLineSkip{\the\baselineskip}
\def\TableCaption{Légende de table}

\begin{tabular}{@{} >{\RaggedRight}p{4cm} *{2}{I{4cm}} @{}}
  \toprule
\mch{Méthode de validation}
    &   \mch{Avantages}   &   \mch{Inconvénients} \\
  \midrule
Resubstitution Validation
    &   \item simple
        \item effortles
        &    \item Surapprentissage                 \\
    \addlinespace
    \bottomrule
\end{tabular}
\end{document}

How can I add a caption after my table and adjust the table's alignment?

Answer 1

For caption is the simplest way to put your table in table float environment and add caption:

\documentclass[a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{array,booktabs}

% added packages and column definitions
\usepackage{ragged2e}           % for smart align of cells' content
    \usepackage{enumitem}       % for nice list
\newlist{tabitemize}{itemize}{1}% <-- defined new list
\setlist[tabitemize]{nosep,     % <-- new list setup
                     topsep     = 0pt       ,
                     partopsep  = 0pt       ,
                     leftmargin = *         ,
                     label      = $\bullet$ ,
                     before     = \vspace{-0.6\baselineskip},
                     after      = \vspace{-\baselineskip}
                     }
\newcolumntype{I}[1]{>{\RaggedRight\arraybackslash             % <-- for lists in columns
                    \tabitemize} p{#1}<{\endtabitemize}}
\newcommand\mch[1]{\multicolumn{1}{c}{\small{#1}}}  % <-- for columns headers

\usepackage{showframe}% for show page layout
\renewcommand*\ShowFrameColor{\color{red}}

\begin{document}

    \begin{table}[htb]
    \centering %%%% <-- for horizontal centering table in text
\begin{tabular}{@{} >{\RaggedRight}p{4cm} *{2}{I{3.6cm}} @{}}
  \toprule
\mch{Méthode de validation}
    &   \mch{Avantages}   &   \mch{Inconvénients} \\
  \midrule
Resubstitution Validation
    &   \item simple
        \item effortles
        &    \item Surapprentissage                 \\
    \bottomrule
\end{tabular}
    \caption{My caption below table} %%%% <-- caption
\label{tab:items}
    \end{table}
\end{document}

Table was slightly wider than text width, therefore I reduce width of last two column. With \centering I horizontally center table in text area.

I delete all not relevant part of your code and add \usepackage{showframe} for showing page layout. In real use this package and following command had to be deleted.