only number some condition in conditional function

Question

Thanks to the answer provided here, however, is it possible that I only number some of the conditions instead all?

Answer 1

\documentclass[margin=3mm, preview]{standalone}
\usepackage{amsmath}
\usepackage{cases}
\begin{document}
\begin{numcases}{f(x)=}
   1 & $x>0$ \label{positive}   \\
   0 & $x=0$ \notag             \\ % <-- not numbered case, you also can use \nonumber
  -1 & $x<0$ \label{negative}
\end{numcases}

See \eqref{positive} or the \eqref{negative} \dots
\end{document}