[Tex/LaTex] Package amsmath Error: \begin{multline} allowed only in paragraph mode

casesequationsmultlinesplit

I am getting an error message when I try to use the multline environment inside cases. This is my equation:

\begin{equation} \label{eq:SMSKIN_TU2009} 
    \begin{split}
        SM_{SKIN,Int} &= SM_{SKIN,Old} + INI - Q_M - EA_{SKIN} + SM_{SKIN,Upd} \\
        SM_{SKIN,New} &= 
        \begin{cases}
            FC_{SKIN}     & 
            \begin{multline}
                \quad \text{if } SM_{SKIN,Int} > FC_{SKIN}, \quad Q_{SKIN} = SM_{SKIN,Int} - \\ FC_{SKIN}
            \end{multline} \\
            0             & \quad \text{if } SM_{SKIN,Int} < 0,  \quad Q_{SKIN} = 0\\
            SM_{SKIN,Int} & \quad \text{otherwise },  \quad Q_{SKIN} = 0\\
        \end{cases}
    \end{split}
\end{equation}

If I don't use the multline environment, the equation is correctly displayed but the compiler throws a warning since the line doesn't fit the page.

I appreciate all your help. Thanks!

Best Answer

As @GuM has suggested, you could load the mathtools package (a superset of the amsmath package) and use its multlined environment instead of the illegal multline environment However, I think you're better off using a simple \parbox to display the material in question.

I would also use \mathit to typeset the multi-letter variable names and \mathrm to typeset the acronyms placed in the subscripts.

\documentclass{article}
\usepackage{mathtools} % for 'dcases' env.
\begin{document}
\begin{equation} \label{eq:SMSKIN_TU2009} 
\begin{split}
\mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} 
&= \mathit{SM}_{\mathrm{SKIN},\mathrm{Old}} + \mathit{INI} 
   - Q_M - \mathit{EA}_{\mathrm{SKIN}} 
   + \mathit{SM}_{\mathrm{SKIN},\mathrm{Upd}} \\
\mathit{SM}_{\mathrm{SKIN},\mathrm{New}} 
&= \begin{dcases}
      \mathit{FC}_{\mathrm{SKIN}} 
         %% set up a parbox with automatic hanging indentation from the 2nd line onward
         &\parbox[t]{6cm}{\raggedright\hangafter1\hangindent1em 
           if $\mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} 
              > \mathit{FC}_{\mathrm{SKIN}}$, 
           $Q_{\mathrm{SKIN}} = 
              \mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} 
              - \mathit{FC}_{\mathrm{SKIN}}$} \\
      0 & \text{if $\mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} < 0$,   
         $Q_{\mathrm{SKIN}} = 0$}\\
      \mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} 
         & \text{otherwise,  $Q_{\mathrm{SKIN}} = 0$}
   \end{dcases}
\end{split}
\end{equation}
\end{document}

Related Solutions

[Tex/LaTex] Error in multline

If you really had to use \left and \right... Additional ones marked.

\documentclass[11pt,twoside,a4paper]{article}
\usepackage{amsmath}
\usepackage{enumerate}
 \begin{document}
  \begin{multline}
 E(y_{i})=
\left(
 x_{2i}'\beta_{2}+
\frac{\sigma}{\Psi\left(
x_{1i}'\beta_{1},\tfrac{x_{2i}'\beta_{2}}{\sigma},\rho
\right)}
\left[
\phi\left(
\tfrac{x_{2i}'\beta_{2}}{\sigma}
\right)\Phi\left(
\tfrac{x_{1i}'\beta_{1}-   \rho\tfrac{x_{2i}'\beta_{2}}{\sigma}}{\left(1-\rho^{2}\right)^{1/2}}
\right)
\right.
\right. % PS
\\
\qquad 
+ \left. 
\left. %PS
\rho\phi(x_{1i}'\beta_{1})\Phi\left(
\tfrac{\tfrac{x_{2i}'\beta_{2}}{\sigma}-\rho x_{1i}'\beta_{1}}{\left(1-\rho^{2}\right)^{1/2}}
\right)
\right]
\right)
\times\Psi\left(
x_{1i}'\beta_{1},\tfrac{x_{2i}'\beta_{2}}{\sigma},\rho
\right)
\end{multline} 
\end{document}

enter image description here

[Tex/LaTex] split equation in multiple lines

I suggest you use a split environment, which in contrast to multline may be used a subenvironment of equation. You need to specify an alignment point on each line with & and separate lines with \\. In this case the first line should be move left relative to the others and the package mathtools provides a convenient command for this:

Sample output

\documentclass{article}

\usepackage{mathtools}

\begin{document}

\begin{equation}
  \label{wave kinematic}
  \begin{split}
    \MoveEqLeft
    \frac{\partial N(\sigma;\lambda;\theta;t)}{\partial t}
    + \frac{\partial C_{g,\lambda}N(\sigma;\lambda;\theta;t)}
    {\partial \lambda} \\
    &+ \cos\phi^{-1} \cdot
    \frac{\partial C_{f,\phi}N(\sigma;\lambda;\theta;t)}{\partial
    \phi} \\
    &+ \frac{\partial C_{f,\theta}N(\sigma;\lambda;\theta;t)}{\partial
    \theta} 
    + \frac{\partial C_{f,\sigma}N(\sigma;\lambda;\theta;t)}{\partial
    \sigma}  
    = \frac{S(\sigma;\theta;\lambda;\varphi;t)}{\sigma}
  \end{split}
\end{equation}

\end{document}

I have split across three lines for clarity. If you wanted to just split in two parts, then multlined (notice the extra d) from the mathtools package would be a simpler solution:

multlined sample

\documentclass{article}

\usepackage{mathtools}

\begin{document}

\begin{equation}
  \label{wave kinematic}
  \begin{multlined}
    \frac{\partial N(\sigma;\lambda;\theta;t)}{\partial t}
    + \frac{\partial C_{g,\lambda}N(\sigma;\lambda;\theta;t)}
    {\partial \lambda} 
    + \cos\phi^{-1} \cdot
    \frac{\partial C_{f,\phi}N(\sigma;\lambda;\theta;t)}{\partial
    \phi} \\
    + \frac{\partial C_{f,\theta}N(\sigma;\lambda;\theta;t)}{\partial
    \theta} 
    + \frac{\partial C_{f,\sigma}N(\sigma;\lambda;\theta;t)}{\partial
    \sigma}  
    = \frac{S(\sigma;\theta;\lambda;\varphi;t)}{\sigma}
  \end{multlined}
\end{equation}

\end{document}

All the above works with elsarticle class in your updated question. E.g. the first version becomes:

\documentclass[authoryear,preprint,review,12pt]{elsarticle}

\usepackage{mathtools}

\begin{document}

\begin{equation}
  \label{wave kinematic}
  \begin{split}
    \MoveEqLeft
    \frac{\partial N(\sigma;\lambda;\theta;t)}{\partial t}
    + \frac{\partial C_{g,\lambda}N(\sigma;\lambda;\theta;t)}
    {\partial \lambda} \\
    &+ \cos\phi^{-1} \cdot
    \frac{\partial C_{f,\phi}N(\sigma;\lambda;\theta;t)}{\partial
    \phi} \\
    &+ \frac{\partial C_{f,\theta}N(\sigma;\lambda;\theta;t)}{\partial
    \theta} 
    + \frac{\partial C_{f,\sigma}N(\sigma;\lambda;\theta;t)}{\partial
    \sigma}  
    = \frac{S(\sigma;\theta;\lambda;\varphi;t)}{\sigma}
  \end{split}
\end{equation}

\end{document}

Best Answer

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[Tex/LaTex] Error in multline

[Tex/LaTex] split equation in multiple lines

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