# ! Misplaced \omit. \multispan ->\omit

I have tried to see if my error is the same as any of the numerous other threads on this forum with the same content, however I cannot seem to find any that match my problem.

When trying to typeset the following code, I am faced with a ! Misplaced \omit. \multispan ->\omit error.

$$\begin{array} {l r@{}l@{} r@{}l@{}} \text{Max} \quad & R &{}\multicolumn{3}{l}{=\log\left(...............\right)} \\ \text{s.t.} \quad & A &{}= B.C.D & E &{}= F.G.H \\ & I &{}= J.K.L & M &{}= N.O.P \\ \end{array}$$


My aim is to have it look like the following:

Max R=log(......)

s.t. A=B.C.D E=F.G.H

I=J.K.L M=N.O.P

where R, A and I are vertically aligned, as are E and M but they are aligned under the contents of the log to save space.

I am presuming the error is due to the alignment tabs and the multicolumn.

The {} group should go inside the \multicolumn; you're forgetting @{} too.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$\begin{array} {l r@{}l@{} r@{}l@{}} \text{Max} \quad & R &\multicolumn{3}{@{}l}{{}=\log\left(...............\right)} \\ \text{s.t.} \quad & A &{}= B.C.D & E &{}= F.G.H \\ & I &{}= J.K.L & M &{}= N.O.P \\ \end{array}$

\end{document}


See Why is $...$ preferable to $$...$$? for reasons why  should never be used in LaTeX.

A different trick:

\documentclass{article}
\usepackage{amsmath}

\newcommand{\multialign}[2]{%
\multispan{#1}\mbox{$\displaystyle#2$}%
}

\begin{document}

\begin{alignat*}{3}
&\textnormal{Max}  \quad & R &\multialign{3}{{}=\log\left(...............\right)} \\
&\textnormal{s.t.} \quad & A &= B.C.D \quad&  E &= F.G.H \\
&&                         I &= J.K.L \quad&  M &= N.O.P
\end{alignat*}

\end{document}


It appears \multicolumn command must appear first in its cell. Your code (completed into a MWE) compiles with {}\multicolumn replaced by \multicolumn and the extra \left removed.

• The problem with removing the {} is that the equals sign between R and log is no longer aligned with the equals signs between A & B and I & J. P.S. that extra \left was accidentally left from what was the contents. I will remove it now. – wilsnunn Jan 10 '16 at 13:13
• \multicolumn{3}{@{}l@{}}{{}=\log\left(..... – user4686 Jan 10 '16 at 13:18

It is not a direct answer to your question, but I would rather use the align environment in that case. The source code and output looks much cleaner to me.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
& \text{Max} & R& =\log\left(\dots\right)\\
& \text{s.t.}& A& = B.C.D & E &= F.G.H\\
&            & I& = J.K.L & M &= N.O.P
\end{align*}
\end{document}