Equation layout when using figure* for long equations occupying two colums

Question

\begin{figure*}[!b]
    \begin{equation}
        XXX
        \label{equ:xequationmodify}
    \end{equation}
\end{figure*}

This is the LaTeX code. I want to display the long equation on two columns and locate it at the bottom of the page. But after compiling, the location is sometimes jumped to several pages behind the right page that I want it to be. Any ideas on how to perfectly solve this question or any other method to display an equation on two columns? Thank you so much for help!

by default figure* does not support b so your figure has no legal placement and will be forced to the end — David Carlisle, Sep 07 '23 at 15:33
The nidanfloat package used to provide for bottom floats in two-column format, but it no longer works properly with the current LaTeX. Maybe you can report it to the package author. — egreg, Sep 07 '23 at 16:14
This answer doesn't recommend a package, and it's ugly, but it works: How to put a full-width table at the top or bottom of the same two-column page as the reference text? — barbara beeton, Sep 07 '23 at 18:20

score 1 · Answer 1 · answered Sep 08 '23 at 10:34

You have not provided the full MWE and we have no information on which document class is in use. If it's the standard article, here's a link to a solution on how to put wide floats in two-column documents based on an extra package multicol.

So, inspired by this answer, you could load multicol packages and place two-column content inside multicols but in a regular one-column document class, s.a. article. This should also work in the report, although this might need some adjustments s.a. using the \chapter outside the multicols.

Note, in the exampe below I used option [twocolumn] and then switched back to \onecolumn. The reason being LaTeX applies a proper layout and give more space for texts.

\documentclass[twocolumn]{article}
\usepackage{mathtools}
\usepackage{microtype}
\usepackage{multicol}
\usepackage[math]{blindtext}
\title{\bfseries The Title}
\author{Author's Name}
\date{}
\begin{document}
\onecolumn
\maketitle
\begin{figure}[b]
  \begin{equation}\label{eq:eq}
    \begin{aligned}
      f(x) ={}& \mbox{Long long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long expression}.
    \end{aligned}
  \end{equation}
\end{figure}
\begin{multicols}{2}
  \Blinddocument
\end{multicols}
\end{document}

On the other hand, if you are asked to use a certain two-column document class such as IEEEtran, the already mentioned stfloat on this site might be a solution. Be wary, if this is a paper to submit, you might not be allowed to do this.

In the next example, a wide equation is placed at the bottom of the first page as long as there's only small content before figure* environment. Otherwise the float is pushed to the next page. I think best appraoch is to make sure figure* is the first thing after \section.

\documentclass{IEEEtran}
% \documentclass[twocolumn]{article}   % or just a standatd two-column article
\usepackage{mathtools}
\usepackage{microtype}
\usepackage{stfloats}
\usepackage[math]{blindtext}
\title{The Title}
\author{Author's Name}
\date{}
\begin{document}
\maketitle
\section{Introduction}
\begin{figure}[b]
  \begin{equation}\label{eq:eq}
    \begin{aligned}
      f(x) ={}& \mbox{Long long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long long long} \
              & + \mbox{Long long long long long long long long long long long long long long long expression}.
    \end{aligned}
  \end{equation}
\end{figure}
\Blinddocument
\end{document}

Equation layout when using figure* for long equations occupying two colums

1 Answers1