How do I get an entire table to get a background color. I dont mean the indivual cells but the entire table to get a gray shade. Something like this:

How do I get an entire table to get a background color. I dont mean the indivual cells but the entire table to get a gray shade. Something like this:

I'd simply put the tabular inside a \colorbox:
\documentclass{article}
\usepackage{booktabs,xcolor,siunitx}
\definecolor{lightgray}{gray}{0.9}
\begin{document}
\begingroup\setlength{\fboxsep}{0pt}
\colorbox{lightgray}{%
\begin{tabular}{l*{4}{S[table-format=3.2]}@{}}
\toprule
Method & \multicolumn{4}{c}{Recognition rate (\%) vs.\ illumination} \\
\cmidrule{2-5}
& \multicolumn{1}{c}{Subset 2} &
\multicolumn{1}{c}{Subset 3} &
\multicolumn{1}{c}{Subset 4} &
\multicolumn{1}{c}{Subset 5} \\
\midrule
Linear subspace [9] & 100.00 & 100.00 & 85.00 & {n/a} \\
Cones-attached [9] & 100.00 & 100.00 & 91.40 & {n/a} \\
Cones-cast [9] & 100.00 & 100.00 & 100.00 & {n/a} \\
PCA & 98.33 & 79.17 & 30.00 & 15.79 \\
LTV${}+{}$PCA & 100.00 & 99.17 & 96.43 & 92.11 \\
Our method${}+{}$PCA & 100.00 & 100.00 & 100.00 & 100.00 \\
\bottomrule
\end{tabular}%
}\endgroup
\end{document}
The local setting of \fboxsep is needed to avoid padding.

I guess you can use the xcolor package as explained here, but instead of set up alternate table row colors, force to color odd and even rows using the same color:
\usepackage[table]{xcolor}
\definecolor{lightgray}{gray}{0.9}
\rowcolors{1}{gray}{gray}
Here is you have a full working example:
\documentclass[11pt]{article}
\usepackage[table]{xcolor}
\definecolor{lightgray}{gray}{0.9}
\begin{document}
\begin{table}[ht]
\caption{default}
\begin{center}
\rowcolors{1}{lightgray}{lightgray}
\begin{tabular}{r|rrrrr}
\hline
& 1 & 2 & 3 & 4 & 5 \\
\hline
1 & 2.36 & 1.08 & -0.49 & -0.82 & -0.65 \\
2 & -0.68 & -1.13 & -0.42 & -0.72 & 1.51 \\
3 & -1.00 & 0.02 & -0.54 & 0.31 & 1.28 \\
4 & -0.99 & -0.54 & 0.97 & -1.12 & 0.59 \\
5 & -2.35 & -0.29 & -0.53 & 0.30 & -0.30 \\
6 & -0.10 & 0.06 & -0.85 & 0.10 & -0.60 \\
7 & 1.28 & -0.46 & 1.33 & -0.66 & -1.80 \\
8 & 0.80 & 0.46 & 1.37 & 1.73 & 1.93 \\
9 & -0.75 & 0.28 & 0.51 & 0.19 & 0.58 \\
10 & -1.64 & -0.12 & -1.17 & -0.10 & -0.04 \\
\hline
\end{tabular}
\end{center}
\end{table}
\end{document}
And the result:

EDIT: Following Mico's comment, there are two limitations:
booktabs package's \toprule,
\midrule, \cmidrule, and \bottomrule commands and@{\extracolsep{\fill}} in the tabular* environment's second argument
-- to force the overall width of the table to be equal to the environment's width argument (usually, but not necessarily,
\textwidth) -- the extra intercolumn whitespace won't be affected by the \rowcolor statement.
booktabs package's \toprule, \midrule, \cmidrule, and \bottomrule commands or (ii) any intercolumn whitespace. E.g., if one specifies @{\extracolsep{\fill}} in the tabular* environment's second argument -- to force the overall width of the table to be equal to the environment's width argument (usually, but not necessarily, \textwidth) -- the extra intercolumn whitespace won't be affected by the \rowcolor statement. :-(
– Mico
Jul 19 '12 at 11:03
The environment {NiceTabular} of nicematrix has a tool to color the whole array (and tools to color rows, columns, cells and block). We keep the ability to use verbatim in the your tabular.
\documentclass{article}
\usepackage{booktabs,xcolor,siunitx}
\usepackage{nicematrix}
\begin{document}
\begin{NiceTabular}{l*{4}{S[table-format=3.2]}@{}}
\CodeBefore
\arraycolor[gray]{0.9}
\Body
\toprule
Method & \multicolumn{4}{c}{Recognition rate (%) vs.\ illumination} \
\cmidrule{2-5}
& \multicolumn{1}{c}{Subset 2} &
\multicolumn{1}{c}{Subset 3} &
\multicolumn{1}{c}{Subset 4} &
\multicolumn{1}{c}{Subset 5} \
\midrule
Linear subspace [9] & 100.00 & 100.00 & 85.00 & {n/a} \
Cones-attached [9] & 100.00 & 100.00 & 91.40 & {n/a} \
Cones-cast [9] & 100.00 & 100.00 & 100.00 & {n/a} \
PCA & \verb|&#&&| & 79.17 & 30.00 & 15.79 \
LTV${}+{}$PCA & 100.00 & 99.17 & 96.43 & 92.11 \
Our method${}+{}$PCA & 100.00 & 100.00 & 100.00 & 100.00 \
\bottomrule
\end{NiceTabular}
\end{document}
You need several compilations (because nicematrix uses PGF/Tikz nodes under the hood).
\newtcbtheorembut Dan's answer does. – schremmer May 27 '16 at 03:01