\jeff{krimmel}

Nice Tabular and Array Spacing in LaTeX

I have struggled for quite some time trying to find a nice way to space entries in the tabular or array environments in LaTeX. I am often in the situation where I have used a fraction in an entry, and the numerator is in contact with the upper horizontal rule and/or the denominator is in contact with the lower horizontal rule. For instance, I get a table that looks like

with the source code

\[
\begin{array}{ll}
\cline{1-2}
\mbox{In the interior} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left( \phi_{i+1,j}
+ \phi_{i-1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\cline{1-2}
\mbox{On the left wall} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left(
2 \phi_{i+1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\cline{1-2}
\mbox{On the right wall} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left(
2\phi_{i-1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\cline{1-2}
\end{array}
\]


I recently solved my problems when I stumbled across the booktabs package for LaTeX. The author writes in the PDF documentation (version 1.61803)

The routines described below are to enable the easy production of tables such as should appear in published scientific books and journals.

The booktabs package has introduced me to commands such ad /toprule, /midrule, and /bottomrule, all of which produce nicely spaced horizontal rules that do not interfere with my table or array entries. I can get output that looks like

with the source code

\[
\begin{array}{ll}
\toprule
\mbox{In the interior} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left( \phi_{i+1,j}
+ \phi_{i-1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\midrule
\mbox{On the left wall} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left(
2 \phi_{i+1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\midrule
\mbox{On the right wall} & \displaystyle
\phi_{i,j} = \frac{1}{4} \left(
2\phi_{i-1,j} + \phi_{i,j+1} + \phi_{i,j-1} \right) \\
\bottomrule
\end{array}
\]


These commands work equally well with the tabular environment. The author is very particular, though, about a couple of rules he has outlined for tables: (1) never use vertical rules, and (2) never use double rules. The booktabs package will not allow you to create nice looking vertical rules (e.g. rules between columns in a table), but you can create double horizontal rules that look okay. This particular package has solved ninety percent of my table and array spacing problems in LaTeX.