cross-referencingsectioningsections-paragraphs
It is well-known that \section environment may be assigned a label \label{refname} and then the refname may be used in order to reference this section:
\section{My nice section}
\label{sec:my-nice-section}
Definitely the section is nice!
\section{My another section}
In the section \ref{sec:my-nice-section} we have discovered that it is nice.
Is there such possibility for \paragraph that we can assign it a label and then reference it?
In general you should be able to do this using the xr package which allows to reference labels in other LaTeX documents.
But the pgfplot package seem to be able to do this now out-of-the-box (manual v1.4.1, section p. 241):
Support for Labels and References In External Files The external library comes with extra support for
\labeland\ref(and other commands which usually store information in the .aux file) inside of external files.
You seem to use an outdated version. At least the mentioned text in section 4.4.2, page 30 isn't there in my (freshly updated) version. There 4.4.2 is on page 42 and is about "Smooth plots".
You could use subequations to number the individual contraints, and tag the whole program with P. At least that is something I've seen in some books:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
a = b
\end{equation}
\renewcommand{\theequation}{P}
\begin{subequations}\label{ip}
\renewcommand{\theequation}{\theparentequation.\arabic{equation}}
\begin{align}
\min &\ cx\label{objective}\\
\text{s.t.}\qquad Ax & \geq b\label{firstConst}\\
Dx & \geq d\label{secondConst}\\
x & \in\{0,1\}\label{binary}
\end{align}
\end{subequations}
\renewcommand{\theequation}{\arabic{equation}}
The binary program~\eqref{ip}, the objective~\eqref{objective}, the constraint~\eqref{firstConst}.
\begin{equation}
c = d
\end{equation}
\end{document}
Best Answer
Sure - if it has a number which can be referenced: