# Equation number in an array

I want to put the equation number at the right for the following code:

$\log{y_{i}} = \left\{ \begin{array}{l l} y_{2i}^{*} & \quad \textrm{if y_{2i}^{*}\succ0}\\ 0 & \quad \textrm{otherwise} \end{array} \right.$


Any idea?

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Do you want the individual elements in the array numbered, or the equation as a whole? –  Werner Oct 25 '13 at 18:43
I want the equation as a whole. –  Metrics Oct 25 '13 at 18:44

Do wisely use {} to maintain readability.

\documentclass[preview,border=12pt]{standalone}
\usepackage{amsmath}
\begin{document}
\abovedisplayskip=0pt\relax% don't use this line in your production
$$\log y_i= \begin{cases} y_{2i}^* & \quad \text{if y_{2i}^*\succ0}\\ 0 & \quad \text{otherwise} \end{cases}$$
\end{document}


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Thanks for the alternative solution –  Metrics Oct 25 '13 at 18:55
@Metrics: It is not the alternative solution but the correct one. align is used when you have more than one equation to be aligned. –  stalking is prohibited Oct 25 '13 at 18:58
@Metrics: Please read align versus equation. –  stalking is prohibited Oct 25 '13 at 19:06
Thank you for the link @Marienplatz –  Metrics Oct 25 '13 at 19:14
flalign should not be used in this case. –  stalking is prohibited Oct 25 '13 at 20:35

load package amsmath and then replace $...$ by

\begin{flalign}
...
\end{flalign}

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Thanks. It worked. –  Metrics Oct 25 '13 at 18:49