Presenting a long linear regression equation

Question

I am using the following code to have a long linear regression model in my two-column latex file. I have used figure * to avoid the overlapping of the equation with the second column. However, it doesn't look good to me. Could you please suggest me any better way for this.

\begin{figure*}[!t]
\begin{equation}
\label{eq:sf}
ua = (49.3) + (-13 * m\_a) + (-0.4 * k\_a) + (-1 * l\_b) + (8 * t\_b) + (-9 * s\_a)
\end{equation}
\end{figure*}

Answer 1

I am not sure exactly what the problem is, but does this help:

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}

\newcommand{\op}{\,*\,}% Use \: instead of \, if you want larger space

\begin{document}
\begin{figure*}[!t]
\begin{align} 
ua = (49.3) + (-13 * m\_a) + (-0.4 * k\_a) \notag\\
    \phantom{=}+ (-1 * l\_b) + (8 * t\_b) + (-9 * s\_a) \label{eq:sf}
\end{align}

\begin{align} 
ua = (49.3) + (-13 \op m\_a) + (-0.4 \op k\_a) \notag\\
    \phantom{=}+ (-1 \op l\_b) + (8 \op t\_b) + (-9 \op s\_a) \label{eq:sf}
\end{align}

\end{figure*}
\end{document}

If you are looking to automatically break the equation that is a bit more complicated, and perhaps the breqn package may be useful to look into.

Answer 2

This may help:

\begin{equation}
  \begin{split}
    ua =&  (49.3) \\
        &+ (-13 * m\_a) \\
        &+ (-0.4 * k\_a) \\
        &+ (-1 * l\_b) \\
        &+ (8 * t\_b) \\
        &+ (-9 * s\_a)
  \end{split}
\end{equation}

You have to \usepackage{amsmath} in the preamble.

The Short Math Guide introduces in page 2 other useful environments for formatting equations.