# Enumerate alignment

Is it possible to improve the alignment of the first item?

\documentclass{article}

\begin{document}

\begin{enumerate}
\item  \begin{tabular}{cccccccccc}
$x[n] =$ & \{1/3 & -1/2 & 1/4 & -1/8 & 1/6\} & and\\
&   &   & $\uparrow$   &   &  &  \\
\end{tabular}
\begin{tabular}{cccccccccc}
$h[n] =$ & \{1 & -1 & 1 & -1\} \\
&    &   &    &   &    &    \\
\end{tabular}
\item \begin{tabular}{cccccccccc}
$x[n] =$ & \{1 & -2 & -3 & 0 & -1\} & and\\
\end{tabular}
\begin{tabular}{cccccccccc}
$h[n] =$ & \{2 & -1/2 & -3 & 1 & -2\} \\
\end{tabular}
\end{enumerate}

\end{document}


The result is:

-
When you have a whole bunch of similarly-aligned tabular columns, use the *{<num>}{<type>} notation. In your case, \begin{tabular}{*{10}{c}}. It's easier to debug and more readable. Also, consider keeping the numerals in math mode, which provides a consistent spacing around the unary operator -. – Werner May 16 '13 at 1:33
What do you want the $\uparrow$ to point from and to? – Pål GD May 16 '13 at 9:24
The \upparrow is a "n = 0" mark. – Papiro May 16 '13 at 9:28

If I understand correctly, you need to add [t] alignment:

\documentclass{article}

\begin{document}

\begin{enumerate}
\item  \begin{tabular}[t]{cccccccccc}        %%%% note [t] here.
$x[n] =$ & \{1/3 & -1/2 & 1/4 & -1/8 & 1/6\} & and\\
&   &   & $\uparrow$   &   &  &  \\
\end{tabular}
\begin{tabular}[t]{cccccccccc}               %%%% and here.
$h[n] =$ & \{1 & -1 & 1 & -1\} \\
&    &   &    &   &    &    \\
\end{tabular}
\item \begin{tabular}{cccccccccc}
$x[n] =$ & \{1 & -2 & -3 & 0 & -1\} & and\\
\end{tabular}
\begin{tabular}{cccccccccc}
$h[n] =$ & \{2 & -1/2 & -3 & 1 & -2\} \\
\end{tabular}
\end{enumerate}

\end{document}


-

The following is a suggestion for a slightly easier notation that is more flexible. Moreover, it provides a consistent and accurate spacing around the math operators you use:

\documentclass{article}
\usepackage{amsmath,xparse}% http://ctan.org/pkg/{amsmath,xparse}
\NewDocumentCommand\printarray{O{~~} >{\SplitList{,}}m}
{%
\def\itemdelim{\def\itemdelim{#1}}% Define list separator with one delay
\ProcessList{#2}{\myitem}% Process list
}
\newcommand\myitem[1]{\itemdelim{#1}}
\begin{document}

\begin{enumerate}
\item $x[n] = \{\printarray{1/3,-1/2,\underset{\uparrow}{1/4},-1/8,1/6}\}$ and $h[n] = \{\printarray{1,-1,1,-1}\}$
\item $x[n] = \{\printarray{1,-2,-3,0,-1}\}$ and $h[n] = \{\printarray{2,-1/2,-3,1,-2}\}$
\end{enumerate}

\end{document}


The "array" is printed using \printarray[<sep>]{<CSV list>} where <sep> defaults to ~~.

Delayed definition of the list separator stems from Package xparse \SplitList last token (or originally Cunning (La)TeX tricks), while amsmath provides \underset.

-

I also would like to suggest you another approach, using a matrix environment instead of a tabular; it's more natural, gives you the desired vertical alignment automatically, and saves you the column format specification:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{enumerate}
\item
$x[n] = \{\begin{matrix} 1/3 & -1/2 & \smash{\underset{\uparrow}{1/4}} & -1/8 & 1/6 \end{matrix}\}$\quad
$h[n] = \{\begin{matrix} 1 & -1 & 1 & -1 \end{matrix}\}$
\item
$x[n] = \{\begin{matrix} 1 & -2 & -3 & 0 & -1 \end{matrix}\}$\quad
$h[n] = \{\begin{matrix} 2 & -1/2 & -3 & 1 & -2 \end{matrix}\}$
\end{enumerate}

\end{document}


-
it also applies math mode automatically, which makes the minus signs behave properly without having to think about them. – barbara beeton May 16 '13 at 12:25

This might be considered cheating, but if you skip the enumeration environment and put everything in one table, things behave better:

\documentclass{article}
\begin{document}
\begin{tabular}{lcccccccccccccccccccc}
1.&$x[n]=$&\{1/3&-1/2&1/4&-1/8&1/6\}& and $h[n]=$&\{1&-1&1&-1\}\\
&&&&&$\uparrow$&&&&&&&&\\
2.&$x[n]=$&\{1&-2&-3&0&-1\}& and $h[n]=$&\{2&-1/2&-3&1&-2\}\\
\end{tabular}
\end{document}


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