# How to create multicolumn with a diagonal line [duplicate]

How to join two columns in a table row and add diagonal line like this:

+-----+--+--+--+
| \ k |  |  |  |
|  \  |  |  |  |
|   \ |  |  |  |
| M  \|  |  |  |
+--+--+--+--+--+
|  |  |  |  |  |
|  |  |  |  |  |
|  |  |  |  |  |
|  |  |  |  |  |
+--+--+--+--+--+
|  |  |  |  |  |
|  |  |  |  |  |
|  |  |  |  |  |
|  |  |  |  |  |
+--+--+--+--+--+


I don't like to answer for my own question. The solution, that created on the base of diagonal lines in table cell is

\usepackage{tikz}
\newcommand\diag[4]{%
\multicolumn{2}{|p{#2}|}{\hskip-\tabcolsep
$\vcenter{\begin{tikzpicture}[baseline=0,anchor=south west,inner sep=#1] \path[use as bounding box] (0,0) rectangle (#2+2\tabcolsep,\baselineskip); \node[minimum width={#2+2\tabcolsep},minimum height=\baselineskip+\extrarowheight] (box) {}; \draw (box.north west) -- (box.south east); \node[anchor=south west] at (box.south west) {#3}; \node[anchor=north east] at (box.north east) {#4}; \end{tikzpicture}}$\hskip-\tabcolsep}}

\begin{table}[htbp]
\centering
\caption{bla bla bla}
\begin{tabular}{|r|r|r|r|r|r|r|r|r|r|r|}
\hline
\diag{.1em}{2.5em}{ $M$ }{ $k$ }  & 1     & 2     & 3     & 4     & 5     & 6     & 7     & 8     & 9 \bigstrut\\
\hline
\multicolumn{1}{|c|}{\multirow{2}[4]{*}{9}} & $\xi_k$ & -0.9682 & -0.8360 & -0.6134 & -0.3243 & 0.0000 & 0.3243 & 0.6134 & 0.8360 & 0.9682 \bigstrut\\
\cline{2-11}    \multicolumn{1}{|c|}{} & $\gamma_k$ & 0.0813 & 0.1806 & 0.2606 & 0.3123 & 0.3302 & 0.3123 & 0.2606 & 0.1806 & 0.0813 \bigstrut\\
\hline
\end{tabular}%