define placement of vertical and horizontal lines in a tabular environment

Question

how can I get rid of the vertical line in the first row? I would like it to only extend from SI to base. While were at it, I also would like to know, if it's possible to define the '\hline' more precisely, say that it only should go from W to E.

I'm still very new to latex so i am not very familiar with lots of packages

This is what I have:

\usepackage{siunitx}
\begin{document}
\begin{tabular}{||c| c c c c c c||}
    \hline
     & W & Q & U & C & E & $\epsilon_0$\\ \hline\hline
    SI & \si{\joule} & \si{\coulomb} & \si{\volt} & \si{\farad} & \si{\volt\per\meter} & \si{\coulomb\per\volt\per\meter}\\ \hline
    base  &
\end{tabular}
\end{document}

Answer 1

Shorter lines in tables can be obtained via \cline which takes two integers separated by a dash in its argument, the first integer denoting the column where the line should start, the second integer denoting the column where the line should end.

However, I think you want to combine such a shorter line with a \hline that spans over all columns. Sadly, \cline{2-7}\hline would not work, but you can make use of the macro \hhline provided by the hhline package:

\documentclass{article}
\usepackage{siunitx}
\usepackage{hhline}
\begin{document}
\begin{tabular}{||c| c c c c c c||}
    \cline{2-7}
    \multicolumn{1}{c|}{} & W & Q & U & C & E & $\epsilon_0$\\ 
    \hhline{-======}
    SI   & \si{\joule} & \si{\coulomb} & \si{\volt} & \si{\farad} & \si{\volt\per\meter} & \si{\coulomb\per\volt\per\meter}\\ 
    \hline
    base &  &  &  &  &  &  \\ 
    \hline
\end{tabular}
\end{document}

If you want to remove the vertical line left of "W", you can go like this:

\documentclass{article}
\usepackage{siunitx}
\usepackage{hhline}
\begin{document}
\begin{tabular}{||c| c c c c c c||}
    \cline{2-7}
    \multicolumn{1}{c}{} & W & Q & U & C & E & $\epsilon_0$\\ 
    \hhline{-======}
    SI   & \si{\joule} & \si{\coulomb} & \si{\volt} & \si{\farad} & \si{\volt\per\meter} & \si{\coulomb\per\volt\per\meter}\\ 
    \hline
    base &  &  &  &  &  &  \\ 
    \hline
\end{tabular}
\end{document}

---

Maybe also have a look at the tabularray package which provides more flexibility when it comes to cell borders (and provides for better spacing in my opinion):

\documentclass{article}
\usepackage{tabularray}
\usepackage{siunitx}
\begin{document}
\begin{tblr}{ 
    colspec = { *{7}{c} },
    hline{1} = {1}{2-Z}{},
    hline{2} = {1}{2-Z}{},
    hline{2-Z} = {2}{1-Z}{},
    vline{1} = {1}{2-Z}{},
    vline{1} = {2}{2-Z}{},
    vline{2,Z} = {1}{1-Z}{},
    vline{Z} = {2}{1-Z}{},
}
         & W & Q & U & C & E & $\epsilon_0$ \\ 
    SI   & \si{\joule} & \si{\coulomb} & \si{\volt} & \si{\farad} & \si{\volt\per\meter} & \si{\coulomb\per\volt\per\meter} \\ 
    base &  &  &  &  &  &  \\ 
\end{tblr}
\end{document}