NiceTabular (NiceMatrix) Empty Line without Vertical Rules

Question

I am trying to add a small, empty line in a NiceTabular environment. The NiceMatrix manual states (Section 5.1.1 The vertical rules):

In the environments of nicematrix, the vertical rules specified by | in the preambles of the environments are never broken, even by an incomplete row or by a double horizontal rule specified by \hline\hline

Which means that the empty line here shows the vertical rules:

\begin{table}[h]
    \small
    \centering
    \begin{NiceTabularX}{\textwidth}{ll}[hvlines]
        \textit{Year}
        &
        \textit{Fruit}
    \\ \hline \hline
        2022
        &
        Apple
    \\
    \end{NiceTabularX}
\end{table}

A quick attempt at a block gave a full-height line that still included the outermost (=border) vertical rules.

\begin{table}[h]
    \small
    \centering
    \begin{NiceTabularX}{\textwidth}{ll}[hvlines]
        \textit{Year}
        &
        \textit{Fruit}
    \\ \Block{1-2}{\hline \hline} \\
        2022
        &
        Apple
    \\
    \end{NiceTabularX}
\end{table}

How can I get a small empty line between rows without any vertical rules?

Answer 1

You can use the rules of the classical {tabular} (of the package array which is loaded by nicematrix).

That means that:

• you use the classical command \hline (and \hline\hline for the double rule);
• you have to define a column type with the behavior of the classical | of array (that classical | of array has been overwritten by nicematrix): \newcolumntype{I}{!{\vrule}} will do the job.

\documentclass{article}
\usepackage{nicematrix}

\begin{document}

\newcolumntype{I}{!{\vrule}}

\begin{table}[h]
\small
\centering
\begin{NiceTabular}{IlIlI}
    \hline
    \textit{Year}
    &
    \textit{Fruit} \\
    \hline\hline
    2022
    &
    Apple \\
    \hline
\end{NiceTabular}
\end{table}

\end{document}

Of course, in that example, there is no point using {NiceTabular} (I would use {tabular}) but you probably want to use other features provided by nicematrix in your real tabular).

---

On the other hand, remember that the main feature of nicematrix is to insert PGF/Tikz nodes under the cells, columns and rows of a classical {tabular}. That means that it's always possible to draw whatever rule you want with Tikz by using those nodes.

\begin{table}[h]
\small
\centering
\renewcommand{\arraystretch}{1.4}
\begin{NiceTabular}{ll}[hvlines]
    \textit{Year}
    &
    \textit{Fruit} \\
    2022
    &
    Apple \\
\CodeAfter
    \tikz \draw [line width = 2 \pgflinewidth] (2-|1) -- (2-|last) ; 
    \tikz \draw [white, shorten > = -1 pt, shorten <= -1 pt] (2-|1) -- (2-|last) ; 
\end{NiceTabular}
\end{table}

\end{document}