How to draw a multirow table?

Question

I am new to Latex and need help drawing tables. Here is what I have right now:

and here is the code for it:

\begin{center}
\begin{tabular}{|c|c|c|c|}
\hline
Topology & Average Delay(s) & Average Bandwidth(kbps) & Hosts \\
\hline
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77  \\ 
\hline
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17  \\
\hline
\caption{This table shows}
\label{eval_table}
\end{tabular}
\end{center}

Here is is what I want to do:

1) Shrink the table width so that it matches the column width

2) Fix the last vertical line

3) Set up the caption properly

I have spent hours on this and I don't know how to fix it.

Answer 1

I'm afraid that because you've provided only a code snippet rather than a full MWE (minimum working example), some vital information -- the width of the text block of your document -- is not available. I've thus had to make some (possibly incorrect) assumptions: A4 paper size, 1-inch margins, two-column mode.

Below is a succession of tables that address various issues you raise. I've deliberately not centered the tables to make it easier to compare the widths of the tables. (In a real document, you should of course encase each tabular environment inside \begin{table} \caption{...} \label{...} \centering [tabular stuff] \end{table} statements.) First, there's a horizontal rule indicating the width of the text block. In the first table, the missing vertical lines are restored by adding a couple of & symbols. Obviously, the table is (much) too wide and won't fit in the available space.

In the second table, the widths of columns 2 and 3 are reduced significantly by moving the unit designations to separate lines. (This should also help reduce any confusion over whether the (s) after Delay is a unit designation or the plural-s to Delay.) In the third table, the width is reduced further, succeeding in making the table fit in the text block. Importantly, all vertical lines are eliminated, allowing some more (horizontal) space saving; in addition, the look of the horizontal lines and the spacing above and below the horizontal lines is improved by replacing the basic LaTeX \hline macro with \toprule, \midrule, and \bottomrule macros.

\documentclass[a4paper,twocolumn]{article}
\usepackage[margin=1in]{geometry}
\usepackage{multirow,booktabs}
\setlength\parindent{0pt}
\begin{document}
Width of text block, two-column mode:
\hrule
\bigskip
(a) Restore the missing vertical lines:

\smallskip
\begin{tabular}{|c|c|c|c|}
\hline
Topology & Average Delay(s) & Average Bandwidth(kbps) & Hosts \\
\hline
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77  & \\ 
\hline
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17  & \\
\hline
\end{tabular}

\bigskip
(b) Reduce table width by moving units designations 
to separate line:

\smallskip
\begin{tabular}{|c|c|c|c|}
\hline
Topology & Average Delay & Average Bandwidth & Hosts \\
& (s) & (kbps) & \\
\hline
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77  & \\ 
\hline
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17  & \\
\hline
\end{tabular}

\bigskip
(c) Better horizontal lines, no vertical lines, reduce table 
width some more:

\smallskip
\begin{tabular}{@{} cccc @{}}
\toprule
Topology & Avg.\ Delay & Avg.\ Bandwidth & Hosts \\
& (s) & (kbps) & \\
\midrule
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77  & \\[2ex]
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17  & \\
\bottomrule
\end{tabular}

\end{document}

Answer 2

Addressing some of your issues:

2. Vertical line

Just add an extra ampersand after the column definition, that'll fix the vertical line. e.g.,

Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77 & \\

The extra vertical lines at the end are addressed by moving the \label block.

3. Caption

The tabular environment, afaik, normally doesn't support captions. You may want to envelope all this with the \begin{table}...\end{table} and place the \caption{Table} after closing the tabular environment.

So, the complete code looks like:

\begin{table}
\centering
\begin{tabular}{|c|c|c|c|}
\hline
Topology & Average Delay(s) & Average Bandwidth(kbps) & Hosts \\
\hline
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77 & \\
\hline 
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17 & \\
\hline
\end{tabular}
\caption{This table shows}\label{eval_table}
\end{table}

producing the following output:

UPD: made some corrections pointed by egreg

Answer 3

As stated in a comment, overuse of rules in a table is considered bad style. Perhaps you prefer this alternative design (which follows the rules and guidelines of the booktab manual):

\documentclass{article}
\usepackage{multirow}
\usepackage{booktabs}
\begin{document}
\begin{table}\centering
\begin{tabular}{cccc}
\toprule
Topology & Average Delay(s) & Average Bandwidth(kbps) & Hosts \\
\midrule
Low & 0.0994 & 2441.85 & \multirow{2}{*}{64} \\
High & 0.1424 & 2515.77 & \\
\addlinespace 
Low & 0.2522 & 1798.60 & \multirow{2}{*}{128} \\
High & 0.1113 & 2123.17 & \\
\bottomrule
\end{tabular}
\caption{This table shows}\label{eval_table}
\end{table}
\end{document}

Which produces: