# column separation lines now showing up in table

I have the following code that produces the table that is shown. What I am trying to do is to get the fourth and fifth column titles vertically aligned at the top. Is this possible?

\documentclass{article}
\usepackage{multirow}
\usepackage{array}

\newcolumntype{x}[1]{%
>{\raggedright\hspace{0pt}}p{#1}}%

\begin{document}
\centering
\renewcommand{\arraystretch}{1.2}
\begin{tabular}{| m{2cm} | p{2cm} | p{2cm} | p{2cm} | p{2cm} | p{2cm} |} \hline
\multirow{3}{1.7cm}{Data Set} &%
\multicolumn{3}{c |}{Raw Data} &%
Offline Processing Time &
Index Size (KB)\\ \cline{2-4}
%
& %
RDF N3 File SizeKB (sec)    &%
Number of Triples &%
Number of Entities\\    \hline
\end{tabular}
\end{document}


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## 2 Answers

Better don't use them (vertical lines) at all!

I think your problem is missing vertical lines. You have to use the ampersands even if those cells are empty, like

Number of Entities & & \\    \hline


You are done as those titles are already aligned at the top.

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Thank you. But I don't understand what you mean by "Better don't use them at all" – ozsu Oct 6 '12 at 23:53
@ozsu have a look at the booktabs package – cmhughes Oct 6 '12 at 23:55
@ozsu: They are not considered as good typographical practice as they reduce readability. See cmhughe's comment above about booktab manual. – Harish Kumar Oct 6 '12 at 23:57
Got it. Learning booktabs is on my list of things to do, but I'm trying to finish a paper first. Thanks much. – ozsu Oct 7 '12 at 0:03

Not sure if this is the desired layout:

\documentclass{article}
\usepackage{multirow}
\usepackage{array}

\newcolumntype{x}[1]{%
>{\raggedright\arraybackslash\hspace{0pt}}p{#1}}%

\begin{document}
\centering
\renewcommand{\arraystretch}{1.2}
\begin{tabular}{| m{2cm} | x{2cm} | x{2cm} | x{2cm} | x{2cm} | x{2cm} |} \hline
\multirow{4}{*}{Data Set} &%
\multicolumn{3}{c |}{Raw Data} &%
\multirow{3}{2cm}{Offline Processing Time} &
\multirow{3}{2cm}{Index Size (KB)}\\ \cline{2-4}
%
& %
RDF N3 File SizeKB (sec)    &%
Number of Triples &%
Number of Entities & &\\    \hline
\end{tabular}
\end{document}


Some remarks: the lines were missing because you didn't complete the columns in the last row (adding the necessary & characters). Also, since you have narrow columns, it is better to have the contents \ragedright, so I changed your p{} columns to x{} columns (adding \arraybackslash).

You should consider not using vertical rules in your tables; the booktabs` package discusses this and helps you to create better looking tables.

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Thanks for fixing this. I was going to use the x{} only after I solved this problem, but I missed the \arraybackslash. Thanks again. – ozsu Oct 7 '12 at 0:04