How to fit long equation in single column?

Question

I am writing a two column document. I am trying to fit following equation in one column.

I read following thread and tried to fit my equation to the given solution but it didn't work

Aligned equations in LaTeX

\documentclass[conference]{IEEEtran}
\usepackage{amsmath,graphicx,amssymb,mathtools,mathdots,bm,fixltx2e}
\usepackage[ansinew]{inputenc}

\begin{align*}
\mathbf{x}^{(m,n)}_{ITI}&= \left[xxxxx \cdots xxxxx xxxxx  \cdots  \\ 
                        &  \hphantom{{}=1 }  xxxxx \right]^T  \notag\\
\end{align*}

\end{document}

---

%-----------error--------------------

! Extra }, or forgotten \right.
<template> }
            $}\ifmeasuring@ \savefieldlength@ \fi \set@field \hfil \endtempl...
l.68 \end{align*}

%-------------------------------------

Answer 1

You can break such an equation while keeping alignment points with a code borrowed from mathtools. I define a \rowvect command that can have as an optional argument \big, \Big, &c.. The optional argument inserts a pair of \bigl…\bigr and the like. It also defines a starred version that inserts a pair of \left…\right.

Demoboth with the classical trick (\left./\right.) and the new command, in which I also propose another alignment:

\documentclass[conference]{IEEEtran}
\usepackage[utf8]{inputenc}
\usepackage{mathtools,graphicx,amssymb,mathtools,mathdots,bm,fixltx2e}

\newcommand\MTkillspecial[1]{% helper macro
\bgroup
\catcode‘\&=9
\let\\\relax%
\scantokens{#1}%
\egroup
}
\DeclarePairedDelimiter\rowvect[]
\reDeclarePairedDelimiterInnerWrapper\abs{star}{
\mathopen{#1\vphantom{\MTkillspecial{#2}}\kern-\nulldelimiterspace\right.}
#2
\mathclose{\left.\kern-\nulldelimiterspace\vphantom{\MTkillspecial{#2}}#3}}

\begin{document}

\begin{align*}
\mathbf{x}^{(m,n)}_{ITI}&=\!\begin{multlined}[t]\left[xxxxx ⋯ xxxxx xxxxx ⋯ \right. \\
                        \left. xxxxx \right] ^T\end{multlined} \\
\mathbf{x}^{(m,n)}_{ITI}&= \!\begin{multlined}[t]\rowvect[\Big]{xxxxx ⋯ xxxxx xxxxx ⋯ \\[-1.5ex] xxxxx}^T\end{multlined} \\
\mathbf{x}^{(m,n)}_{ITI}&= \rowvect[\Big]{xxxxx ⋯ xxxxx xxxxx ⋯ \\[-1.5ex] & \hphantom{{}=1 } xxxxx}^T\
\end{align*}

\end{document}