[Tex/LaTex] Equation environment for centered, equally-spaced columns of expressions

amsmathhorizontal alignmentmath-mode

I want a environment for displaying rows and columns of mathematical expressions, such that the contents of each column is centered, and the columns are equally spaced. Rows must have optional equation numbers, as with the align* environment.

I posted a similar question a few months ago, answered here:
Standard math environment for equally-spaced columns of expressions?

Although I accepted the answer there at the time, it has some shortcomings: I have to specify in advance how many columns I'm going to need (unlike the existing align* environment, for example), and it doesn't allow me to have equation numbers for rows in a straightforward way.

Edit on 3rd April 2012: The syntax has to be like this:

\begin{newenvironment}
A & B & C
\\
\nonumber
f & g & h
\end{newenvironment}

This should produce two lines of displayed mathematics in three columns, all equally-spaced from the page margins and from each other. The first line should have an equation number, the second shouldn't.

Best Answer

Ok, the following is probably as dirty as it could ever get, and I have to admit I patched it together by trial&error, but at least it might invoke the spirits-that-be to find a better solution.

Try

\documentclass{article}

\usepackage{amsmath}

\usepackage{etoolbox}

\makeatletter
\def\calign@preamble{%
   &\hfil\strut@
    \setboxz@h{\@lign$\m@th\displaystyle{##}$}%
    \ifmeasuring@\savefieldlength@\fi
    \set@field
    \hfil
    \tabskip\alignsep@
}
\let\cmeasure@\measure@
\patchcmd\cmeasure@{\divide\@tempcntb\tw@}{}{}{}
\patchcmd\cmeasure@{\divide\@tempcntb\tw@}{}{}{}
\patchcmd\cmeasure@{\ifodd\maxfields@
  \global\advance\maxfields@\@ne
  \fi}{}{}{}    
\newenvironment{calign}
{%
  \let\align@preamble\calign@preamble
  \let\measure@\cmeasure@
  \align
}
{%
  \endalign
}  
\makeatother

\begin{document}

\begin{calign}
  A & \min(B,Z) & C
\\
\nonumber
f & g & h
\end{calign}

\end{document}

calign example

Related Solutions

[Tex/LaTex] Right Align Equation Number with hfill in Custom Environment

You can use tabular*, with an \extracolsep{\fill} to move the last column to the right margin, as in:

\documentclass[12pt]{article}

\begin{document}

Here's some text. Here's some text. Here's some text. Here's some
text. Here's some text. Here's some text. Here's some text. Here's
some text. Here's some text. Here's some text. Here's some
text. Here's some text.
\begin{center}
  \begin{tabular*}{1.0\linewidth}{@{}ccc@{\extracolsep{\fill}}r@{}}
    One& Two& Three& Number 1\\
    Four& Five& Six& Number 2
  \end{tabular*}
\end{center}

\end{document}

That gives you: enter image description here

(If you don't want it flush with the left margin, you can add an \hskip to that initial @{}.)

[Tex/LaTex] Standard math environment for equally-spaced columns of expressions

For equally-spaced columns (different from equal-width columns), you could put your contents in a fixed-width tabular* environment:

\documentclass{article}
\usepackage{lipsum,array,amsmath}
\begin{document}
\lipsum[1]
\newcolumntype{E}{@{}c@{}}% begin-/end-column definitions
\noindent\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}E*{3}{>{$}c<{$}}E}
  & x+y & e^{2 \pi i} & \sigma & \\& \text{First} & \text{Second} & \text{Third} &
\end{tabular*}
\lipsum[2]
\end{document}

I define a new columntype E used merely as a spacer for the first/last columns. Also, the addition of @{\extracolsep{\fill}} adds stretch before/after each column to space things out evenly across \textwidth. Using *{3}{>{$}c<{$}} allows for 3 similarly defined columns (centered c and typeset in math mode $...$ ).

Equal-spaced columns in tabular*

Of course, this requires you to know how many columns you want to typeset, since you're using the tabular* environment. Although this is not as noticeable, you might want to add \renewcommand{\tabcolsep}{0pt} and scope {...} it around your tabular* environment in order to remove the spacing caused by the E column type. For example the code

\newcolumntype{E}{@{}c@{}}% begin-/end-column definitions

{\renewcommand{\tabcolsep}{0pt}% No \tabcolsep
\noindent\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}E*{3}{>{$}c<{$}}E}
  & x+y & e^{2 \pi i} & \sigma & \\ & \text{First} & \text{Second} & \text{Third} &
\end{tabular*}}

\noindent\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}}E*{3}{>{$}c<{$}}E}
  & x+y & e^{2 \pi i} & \sigma & \\& \text{First} & \text{Second} & \text{Third} &
\end{tabular*}

produces this marginal difference

$Small adjustments to tabular* environment columns via \tabcolsep$

Best Answer

Related Solutions

[Tex/LaTex] Right Align Equation Number with hfill in Custom Environment

[Tex/LaTex] Standard math environment for equally-spaced columns of expressions

Related Question