Combine 4 cells in a table

Question

Here is a simple table.

I want to merge 4 cells. I want to combine the three "this" cells area in this table.
I thought I have to use multirow and multicolum at same time.
However, I could not find how to use it.

If possible, could you post the modified LaTeX source code?

My LaTeX code:

\documentclass{article}
\usepackage{multirow}% http://ctan.org/pkg/multirow
\usepackage{hhline}% http://ctan.org/pkg/hhline
\begin{document}

\begin{table}[ph]
\begin{center}
\begin{tabular}{c|c|c|c|c}
\hline
\multirow{2}{*}{Raaa (k)} & \multicolumn{4}{c}{C ()} \\
\hhline{~----}
 & 3.3 & 2.5 & 1 & 0.5 \\
\hline
\multirow{2}{*}{Raaa (k)} & \multirow{2}{*}{this} & this & 0.5 & 0.6\\
\hhline{~~~--}            &                       & this & 0.7 & 1.2 \\
\hline
\end{tabular}
\caption{R, C ripple size}
\label{T:peak}
\end{center}
\end{table}
\end{document}

Answer 1

Both rows should contain a \multicolumn{2}{c|}{...}, and the first row should contain a nested \multirow{2}{*}{...}:

\documentclass{article} 
\usepackage{multirow}% http://ctan.org/pkg/multirow
\usepackage{hhline}% http://ctan.org/pkg/hhline
\begin{document}
\begin{table}[ph]
  \centering
  \begin{tabular}{c|c|c|c|c}
    \hline
    \multirow{2}{*}{Raaa (k)} & \multicolumn{4}{c}{C ()} \\
    \hhline{~----}
    & 3.3 & 2.5 & 1 & 0.5 \\
    \hline
    \multirow{2}{*}{Raaa (k)} & \multicolumn{2}{c|}{\multirow{2}{*}{this}} & 0.5 & 0.6\\
    \hhline{~~~--}            & \multicolumn{2}{c|}{}                      & 0.7 & 1.2 \\
    \hline
  \end{tabular}
  \caption{R, C ripple size}
  \label{T:peak}
\end{table}
\end{document}

Since \multicolumn overrides any of the set column alignments (including the vertical rules), you have to respecify everything. Hence the use of c| to center the contents and end it with a vertical rule.

Also note how I used \centering instead of the center environment (\begin{center} ... \end{center}). This allows for better vertical spacing around elements in your document. Consider reading the following post: Should I use center or centering for figures?

Answer 2

Vertical lines burn my eyes. Tables almost always look better without them. Here's a version that uses booktabs for nice horizontal lines.

\documentclass{article} 
\usepackage{multirow}
\usepackage{booktabs}
\begin{document}

\begin{table}[ht]
\centering
\begin{tabular}{ccccc}
  \toprule
    \multirow{2}{*}{Raaa (k)} & \multicolumn{4}{c}{C ()} \\
    \cmidrule{2-5} & 3.3 & 2.5 & 1 & 0.5 \\
  \midrule
    \multirow{2}{*}{Raaa (k)} & \multicolumn{2}{c}{\multirow{2}{*}{this}} & 0.5 & 0.6 \\
    \cmidrule{4-5}            & \multicolumn{2}{c}{}                      & 0.7 & 1.2 \\
  \bottomrule
\end{tabular}
\caption{R, C ripple size}
\end{table}

\end{document}

Which gives you this:

Answer 3

Here is a way to construct that table with {NiceTabular} of nicematrix (however, as many people on this site, I recommend constructing such tables with the design of booktabs).

\documentclass{article}
\usepackage{nicematrix}
\begin{document}
\begin{table}[ph]
\begin{center}
\begin{NiceTabular}{c|c|c|c|c}[hlines]
\Block{2-1}{Raaa (k)} & \Block{1-4}{C ()} \
                      & 3.3               & 2.5  & 1   & 0.5 \
\Block{2-1}{Raaa (k)} & \Block{2-1}{this} & this & 0.5 & 0.6 \
                      &                   & this & 0.7 & 1.2 \
\end{NiceTabular}
\caption{R, C ripple size}
\label{T:peak}
\end{center}
\end{table}
\end{document}