# labelling arrays

Sorry if this is stupid but writing

$$\begin{array}{c} \label{cycle LP} \text{min} \ \ \ w^t x \\ \text{s.t.} \sum_{C \in \mathcal{C}} x_v \geq 1 \\ x \geq 0 \end{array}$$

the label does not appear how do I make the label appear?

Hope you meant label is the equation number, if yes, please try with the following code:

\documentclass{book}
\usepackage{mathtools}
\begin{document}

$$\label{cycle LP} \begin{split} \min w^t x \\ \text{s.t.} \sum_{C \in \mathcal{C}} x_v \geq 1 \\ x \geq 0 \end{split}$$

PS: Don't use $$for unnumbered equations, it was one of an old PlainTeX tags. please use $...$ instead of$$

• can arrays not be labelled? I guess multiline equation is pretty similar but the non centering is a bit annoying – Hao S Sep 3 at 16:02
• @HaoS Agreed... – MadyYuvi Sep 4 at 4:53
• @HaoS - You asked, "can arrays not be labelled"? Short answer: No. Longer answer: Not unless you create an entire new code superstructure -- which does not exist by default in either the LaTeX kernel or any of the main LaTeX document classes. Incidentally, is there a reason for not wishing to cross-reference a displayed equation that contains the array environment of interest? – Mico Oct 3 at 6:15