Math & Science ⇒ Counterpart to \nonumber

[achim]

Hi all

I was wondering about this for a while:

In equations, it's easy to suppress the numbering with the \nonumber command. But how can one only have one equation numbered in a environment like:

Code: Select all

\begin{align*}
    ...
\end{align*}

?

E.g.:

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\documentclass{article}

\usepackage[sumlimits, intlimits]{amsmath}      %Math Type setting
\usepackage{amsfonts}                           %Math Fonts

\begin{document}


\begin{align}
	w(s, \tau) &= \sum_j^n \Phi_{Wj}(s) q_{wj}(\tau) = \mathbf{\Phi}_W^T(s) q_W(\tau) \nonumber \\
	\theta(s, \tau) &= \sum_j^n \Phi_{Tj}(s) q_{Tj}(\tau) = \mathbf{\Phi}_T^T(s) q_T(\tau)
\end{align}

\hrule

\begin{align*}
	w(s, \tau) &= \sum_j^n \Phi_{Wj}(s) q_{wj}(\tau) = \mathbf{\Phi}_W^T(s) q_W(\tau) \\
	\theta(s, \tau) &= \sum_j^n \Phi_{Tj}(s) q_{Tj}(\tau) = \mathbf{\Phi}_T^T(s) q_T(\tau) % \number or so?
\end{align*}

\end{document}

Is there a counterpart to \nonumber?

Cheers

[frabjous]

I think the normal way of dealing with this is just to use \nonumber or \notag on all the lines you don't want numbered with an align environment. If you're set on using align*, I suppose you could use \refstepcounter{equation}\tag{\theequation} though it feels a bit hacky.

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\begin{align*}
   w(s, \tau) &= \sum_j^n \Phi_{Wj}(s) q_{wj}(\tau) = \mathbf{\Phi}_W^T(s) q_W(\tau) \\
   \theta(s, \tau) &= \sum_j^n \Phi_{Tj}(s) q_{Tj}(\tau) = \mathbf{\Phi}_T^T(s) q_T(\tau) \refstepcounter{equation}\tag{\theequation}
\end{align*}

Also, if the idea behind this is that there should be a single reference number assigned to the whole series of equations, then consider using an aligned environment (inside another math environment) instead, e.g.:

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\begin{equation}
\begin{aligned}
   w(s, \tau) &= \sum_j^n \Phi_{Wj}(s) q_{wj}(\tau) = \mathbf{\Phi}_W^T(s) q_W(\tau) \\
   \theta(s, \tau) &= \sum_j^n \Phi_{Tj}(s) q_{Tj}(\tau) = \mathbf{\Phi}_T^T(s) q_T(\tau) 
\end{aligned}
\end{equation}

(The single number is thus centered in the middle.)

[achim]

I was in fact trying to have only one equation numbered in the align* environment (as you correctly addressed in the first part of your answer) and not have the number centred over the environment.
Of course there is no reason not to use the \nonumber if the align* only holds a few equations. It's rather handy though if there are more equations in it. Specifically I'm thinking of the situation where one uses the \intertext{...} in order to have all equations in a section aligned equally. Anyway, this could be a follow up question. It's quite cumbersome to use the \intertext{} all the time within an align environment. Is there an easier way to maybe 'synchronise' all the align environments?

As for the numbering, It's probably a good idea to define a new command:

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\newcommand{\eqnumbering}{%
    \refstepcounter{equation}\tag{\theequation}
    }

Thanks for the help frabjous!