Using align property for equations without numbering, when referencing other equation number

Question

I am trying to create a master list of equations (called 'Models'), which are then referenced in main text (the idea is that not all the equations in the master list appear in the main text). I would like it so the equation numbering is based upon the order in the master list.

This is set fine for equations using \begin{equation}, but when I use the \begin{align} it continues to number the equation in the main text, and gives the name of the referenced equation in brackets.

I would like help with being able to set the 'Utility of gamble' equation in the same way as a the 'Softmax' equation.

Thank you!

\documentclass[english,natbib]{report}
\usepackage{amssymb}                            
\usepackage{amsmath}                    
\newcommand{\eqname}[1]{\tag*{#1}}

\begin{document}

\begin{align}
&U_{gamble} = 0.5(V_{gain})^{again} - 0.5(-V{loss})^{aloss}\\ \nonumber
&U_{certain} = (V_{certain})^{again} & &if\ V_{certain}\geq 0\\ \nonumber
&U_{certain} = (-V_{certain})^{aloss} & &if\ V_{certain}>0 \\ \nonumber \tag{\ref{equation:decision_gambles}}
\end{align}

\begin{equation}
P_{gamble} = \frac{1}{1+e^{-\mu(U_{gamble}-U{certain})}}
\tag{\ref{equation:decision_softmax}}
\end{equation}    

\subsection{Models}

\begin{flalign}
&U_{gamble} = 0.5(V_{gain})^{again} - 0.5(-V{loss})^{aloss} \\ \nonumber
&U_{certain} = (V_{certain})^{again} & &if\ V_{certain}\geq 0 \\ \nonumber
&U_{certain} = (-V_{certain})^{aloss} & &if\ V_{certain}< 0 \\ \nonumber
\label{equation:decision_gambles} \\ \eqname{\textbf{Utility of Gambles}}
\end{flalign}

\begin{flalign}
P_{gamble} = \frac{1}{1+e^{-\mu(U_{gamble}-U{certain})}} &&
\label{equation:decision_softmax} \\ \eqname{\textbf{Softmax}}
\end{flalign}

\end{document}

Answer 1

In my comment I had the impression that you would like to suppress the numbering, but in fact you want to repeat it, don't you ? Hence you can't use the stared version, an actually need the \nonumber on the lines that should not be numbered.

As far as I can understand your aim, this code does the job:

\documentclass[a4paper]{report}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amssymb}
\usepackage{amsmath}

\begin{document}

\begin{align}
&U_{gamble} = 0.5(V_{gain})^{again} - 0.5(-V{loss})^{aloss} \tag{\ref{equation:decision_gambles}}\\ 
&U_{certain} = (V_{certain})^{again} & &if\ V_{certain}\geq 0 \nonumber\\
&U_{certain} = (-V_{certain})^{aloss} & &if\ V_{certain}>0 \nonumber 
\end{align}


\begin{equation}
P_{gamble} = \frac{1}{1+e^{-\mu(U_{gamble}-U{certain})}}
\tag{\ref{equation:decision_softmax}}
\end{equation}
%%

\subsection{Models}

\begin{align}\label{equation:decision_gambles} 
&U_{gamble} = 0.5(V_{gain})^{again} - 0.5(-V{loss})^{aloss} \\
&U_{certain} = (V_{certain})^{again} & &if\ V_{certain}\geq 0 \nonumber\\
&U_{certain} = (-V_{certain})^{aloss} & &if\ V_{certain}< 0 \nonumber\\
\nonumber \\
&&&\tag*{\textbf{Utility of Gambles}}
\end{align}

\begin{align}\label{equation:decision_softmax}
P_{gamble} = \frac{1}{1+e^{-\mu(U_{gamble}-U{certain})}}& \\
  &\tag*{\textbf{Softmax}}
\end{align}
\end{document}