# Diagonal line for a table with multiple rows

Considering the answer of question, I used the slashbox package to draw a diagonal line. But the problem is I have multiple rows in my table and that makes the line not aligned well within the cell corners. It also gives wierd spaces between cells:

\documentclass{article}
\usepackage{slashbox}

\begin{document}

\begin{table}[!htpc]
\begin{center}
\centering
\caption{some table.}
\label{possibility}
\begin{footnotesize}

max width=\textwidth}{
\begin{tabular}{|c|c|c|c|c|c|c|c|c|}

\hline
% after \\: \hline or \cline{col1-col2} \cline{col3-col4} ...
&first  & first  & second  & second & both  & both  & &\\
&key & key &  key &  key& key & key & none&all\\
\backslashbox{Room}{Date}  &at & at &  at &  at & at & at& & \\
&d & p &  d & p & d & p & &\\ \hline
$C_1$&Y & N & N & N & N & N & N &N \\ \hline

\hline

\end{tabular}
}
\end{footnotesize}
\end{center}
\end{table}

\end{document}


EDIT

I have used the answer presented by @bernard but it gives me ! Use of \line doesn't match its definition as an error. Not sure if it would happen for others as well.

It's better to use diagbox, which is more powerful. I improved your table using makecell (allows for line breaks and vertical padding in cells). Also, don't use the center environment in tables, as it adds unwanted vertical spacing; use \centering instead. The placement of the diagonal line is adjusted through the optional argument of \multirow.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{diagbox}
\usepackage{caption, multirow, makecell}
\setcellgapes{3pt}

\begin{document}

\begin{table}[!htp]
\centering
\caption{some table.}
\label{possibility}
\footnotesize\makegapedcells
max width=\textwidth}{
\begin{tabular}{|*{9}{c|}}
\hline
\multirowcell{5.2}[2.3ex]{\diagbox[height=5.17\line]{\rlap{\enspace\raisebox{2ex}{Room}}}{\raisebox{-3.5ex}{Date}}} &\makecell{first\\key} & \makecell{first\\key} & \makecell{second\\key} & \makecell{second\\key} & \makecell{both\\keys} & \makecell{both\\keys}& none&all\\
& at & at & at & at & at & at & & \\
& d & p & d & p & d & p & & \\ \hline
$C₁$ & Y & N & N & N & N & N & N & N \\
\hline
\end{tabular}
}
\end{table}

\end{document}


• Always vote +1 for my friends. – Sebastiano May 16 '17 at 9:02
• Why did you comment out the adjustbox? – lonesome May 16 '17 at 9:43
• @lonesome: Sorry. I did it to see whether the table overflowed the prescribed dimensions, and I forgot to uncomment before posting. – Bernard May 16 '17 at 9:50
• It also gives error as ! Use of \line doesn't match its definition. – lonesome May 16 '17 at 9:50
• I asked about adjustbox just in case if it was a wrong choice. – lonesome May 16 '17 at 9:51