How to use the inline equation format in the equation environment

Question

I have a very long equation and have to use a equation environment to get a equation number. But I still want the equation to use the inline equation format, which automatically do line breaks and is more compact than manually doing break lines.

Here is the test tex:

\documentclass[twocolumn]{article}

\begin{document}

Equation \ref{eq1}.

$f=a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c$

\begin{equation}\label{eq1}
f=a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c
\end{equation}

\end{document}

I want the following:

Update: I want the equation to be citeable using label and ref command. This is also why　Ｉ　ｎｅｅｄ　ｔｈｅ　ｅｑｕａｔｉｏｎ　ｅｎｖｉｒｏｎｍｅｎｔ．

Answer 1

\documentclass[twocolumn]{article}

\begin{document}



\begin{center}
\refstepcounter{equation}$f=a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c$\\
\hspace*{\fill}(\theequation)
\end{center}


\end{document}

Answer 2

You can define a longequation environment:

\documentclass[twocolumn]{article}

\usepackage{lipsum} % just for the example

\newenvironment{longequation}
 {\begin{equation}\begin{minipage}{.9\columnwidth}$}
 {$\end{minipage}\end{equation}}

\begin{document}

Equation \ref{eq1}.

\lipsum*[2]
\begin{longequation}\label{eq1}
f=a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+
c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+f+a+b+c+d+e+
f+a+b+c+d+e+f+a+b+c
\end{longequation}
\lipsum[3]

\end{document}