[Tex/LaTex] Multiple subequation labels in one \ref

cross-referencingequationsnumbering

I'm trying to write a macro that puts subequations' labels in parentheses in a compact form. For example, if I have

\begin{subequations}
\begin{align}
    y - ax &= b \label{subeq1}\\
    x^2 + y^2 &= r^2 \label{subeq2}
\end{align}
\end{subequations}

with the two equations being tagged as (1a) and (1b), then I want to be able to type \ref{subeq1,subeq2} and get (1a,b). Similarly, if I have three subequations, say (2a), (2b) and (2c) with labels subeq3, subeq4 and subeq5 respectively, then I want to be able to type \ref{subeq3,subeq4,subeq5} and get (2a–c). I would like this to work for any number of subequations.

Best Answer

This isn't exactly what you wanted but is close.

enter image description here

Note:

The latest version (V0.18) is not yet on CTAN, but can be obtained from Toby Cubitt's site. Though it does no appear to make a difference in this particular example.

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{cleveref}% load last


\crefname{equation}{equation}{equations}
\Crefname{equation}{Equation}{Equations}% For beginning \Cref
\crefrangelabelformat{equation}{(#3#1#4--#5#2#6)}

\crefmultiformat{equation}{equations (#2#1#3}{, #2#1#3)}{#2#1#3}{#2#1#3}
\Crefmultiformat{equation}{Equations (#2#1#3}{, #2#1#3)}{#2#1#3}{#2#1#3}

\begin{document}

\begin{subequations}
\begin{align}
    y - ax &= b \label{eq:subeq1}\\
    x^2 + y^2 &= r^2 \label{eq:subeq2}\\
    x^2 + y^2 &= r^2 \label{eq:subeq3}\\
    x^2 + y^2 &= r^2 \label{eq:subeq5}
\end{align}
\end{subequations}

\noindent
For the case where the label is part of a sentence:\par
Once referenced: \cref{eq:subeq1}\par
Two referenced: \cref{eq:subeq1,eq:subeq2}\par
Three referenced: \cref{eq:subeq1,eq:subeq2,eq:subeq3}\par

\bigskip
\noindent
For the case where the labels beign a sentence:\par
\Cref{eq:subeq1} is one equations.\par
\Cref{eq:subeq1,eq:subeq2} are two equations.\par
\Cref{eq:subeq1,eq:subeq2,eq:subeq3} are three equations.
\end{document}

Related Solutions

[Tex/LaTex] redefining \label and \ref when using hyperref

Because some redefining of \label/\ref by hyperref/nameref is done via \AtBeginDocument, you have to use it also at a later time after the packages are loaded:

\usepackage{hyperref}
\usepackage{letltxmacro}

\AtBeginDocument{%
  \LetLtxMacro{\TheRealLabel}{\label}%
  \LetLtxMacro{\TheRealRef}{\ref}%
  \LetLtxMacro{\TheRealPageRef}{\pageref}%
  % redefining \label, \ref, \pageref (\renewcommand or \DeclareRobustCommand)
}

Updated with egreg's comment. \LetLtxMacro of package letltxmacro takes care of macros that are defined via \DeclareRobustCommand (or as macros with optional parameters).

[Tex/LaTex] Labels in subequations

This requirement may require many manual tags,

\documentclass{book}
\usepackage{amsmath}

\begin{document}

 \begin{subequations}\label{eq}
    \begin{align}
    &\alpha_x = \dots\label{eqa}\\
    &\beta_x = \dots\label{eqb}\\
    &\gamma_x = \dots\label{eqc}
    \end{align}
    \end{subequations}
\vspace{-\belowdisplayskip}
\vspace{-\abovedisplayskip}
\setcounter{equation}{3}
\renewcommand{\theequation}{\theparentequation\alph{equation}}
 \begin{subequations}\label{eqd}
   \begin{align}
    &\delta_x = \dots \quad\quad \mbox{if
    $\dots$}\label{eqd1}\tag{1d-1}\\
    &\delta_x = \dots \quad\quad \mbox{if
    $\dots$}\label{eqd2}\tag{1d-2}\\
    &\delta_x = \dots \quad\quad \mbox{if
    $\dots$}\label{eqd3}\tag{1d-3}
    \end{align}
    \end{subequations}

\setcounter{equation}{1}
\renewcommand{\theequation}{\arabic{equation}}
Trial \ref{eqd}\quad \ref{eqd3}
\begin{align}
a+b=c
\end{align}

\end{document}

I am not sure whether this suggestion is the correct way to do (if not suits then leave this)...