[Tex/LaTex] Aligning equations in a cases environment

cases

In my work, I am trying to typeset the following system of equations.

\begin{equation*}
\begin{cases}
\pi_n  (i) = {n^2}/{\vol(G_n)} \cr
\pi_n (j) =  {n}/{\vol(G_n)} \cr
q^{(n)}_{ij} = {1}/{n^2 } \cr
q^{(n)}_{ji} = {1}/{n}
\end{cases}
\end{equation*}

However, I would like to align the equal signs. If I do this by adding ampersands (see below), too much space is added before the equal signs, which makes the system of equations look worse than before. Is there any other non-manual way to align the equations?

\begin{equation*}
\begin{cases}
\pi_n  (i) &= {n^2}/{\vol(G_n)} \cr
\pi_n (j) &=  {n}/{\vol(G_n)} \cr
q^{(n)}_{ij} &= {1}/{n^2 } \cr
q^{(n)}_{ji} &= {1}/{n}
\end{cases}
\end{equation*}

Example of the problem

Best Answer

I think that you want to use \left\{...\right. around your equation. To be able to align your equations inside these you can use the split environment from the amsmath package.

EDIT

In the comments both above and below the consensus is that the aligned environment is superior to split in this situation. Perhaps I am missing it but I can't see the difference in this example, however, as people more knowledgeable than I are advocating using the aligned environment there must be cases where it does matter.

Here is a comparison of the two environments for this example:

enter image description here

This produces:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator\vol{\text{vol}}
\begin{document}
\[\left\{
  \begin{aligned}
    \pi_n  (i) &= {n^2}/{\vol(G_n)} \cr
    \pi_n (j) &=  {n}/{\vol(G_n)} \cr
    q^{(n)}_{ij} &= {1}/{n^2 } \cr
    q^{(n)}_{ji} &= {1}/{n}
  \end{aligned}\right.\tag{\textbf{aligned}}
\]

\[\left\{
  \begin{split}
    \pi_n  (i) &= {n^2}/{\vol(G_n)} \cr
    \pi_n (j) &=  {n}/{\vol(G_n)} \cr
    q^{(n)}_{ij} &= {1}/{n^2 } \cr
    q^{(n)}_{ji} &= {1}/{n}
  \end{split}\right.\tag{\textbf{split}}
\]

\end{document}

Related Solutions

[Tex/LaTex] Left aligning and breaking equations in cases environment

I'd suggest using mathtools and its dcases and multlined environments.

I propose two solutions; the first avoids an ambiguity in your formulas, where the same index is used both as a bound and a free variable; the second one is similar to yours.

I removed the unnecessary \left and \right; changed \Bigg into \biggl and \biggr; changed \text{ : } into simple colons; defined \argmin.

\documentclass{article}

\usepackage{amsmath,mathtools}

\newcommand{\diff}{\mathop{}\!d}
\DeclareMathOperator*{\argmin}{arg\,min}

\begin{document}

\begin{equation}
\begin{dcases}
u_j^{k+1}(x)=
  \!\begin{multlined}[t]
  \argmin_{u}
  \biggl\{
  \frac{\mu}{2}\int\limits_{\Omega} (u_j(x)-m(x))^2\diff x \\
  +\sum_{i=1}^{N}\biggl(
     \lambda\int\limits_{\Omega} r_i(x)u_i(x)\diff x 
     + \frac{\gamma}{2}\int\limits_{\Omega} (u_i(x)-m(x))^2\diff x
   \biggr)
  \biggr\},
  \end{multlined}
\\[1ex]
f'(x_{0})=0 : z=f(x_{0}) \text{ is de horizontale raaklijn.}
\\[1ex]
\lim_{x\to x_{0}} f'(x)=\pm\infty : x=x_{0} \text{ is de verticale raaklijn.}
\\[1ex]
g(x_{0}){R}_{0} : z-f(x_{0})=f'(x_{0})\cdot(x-x_{0})
  \text{ is de raaklijn.}
\end{dcases}
\end{equation}

\begin{equation}
\begin{dcases}
\!\begin{aligned}[t]
u_j^{k+1}(x)&=
  \argmin_{u}
  \biggl\{
  \lambda\sum_{i=1}^{N}\int_{\Omega} r_i(x)u_i(x)\diff x \\
  &\quad+ \frac{\gamma}{2} \sum_{i=1}^{N}\int_{\Omega} (u_i(x)-m(x))^2\diff x 
  + \frac{\mu}{2}\int_{\Omega} (u_i(x)-m(x))^2\diff x
  \biggr\},
  \end{aligned}
\\[1ex]
f'(x_{0})=0 : z=f(x_{0}) \text{ is de horizontale raaklijn.}
\\[1ex]
\lim_{x\to x_{0}} f'(x)=\pm\infty : x=x_{0} \text{ is de verticale raaklijn.}
\\[1ex]
g(x_{0}){R}_{0} : z-f(x_{0})=f'(x_{0})\cdot(x-x_{0})
  \text{ is de raaklijn.}
\end{dcases}
\end{equation}

\end{document}

Nested right cases

Here is what you can do with the package cascade.

\documentclass{article}
\usepackage{geometry}
\usepackage{cascade,calc}

\begin{document}


\Cascade
  {}
  {
    \Cascade
      {}
      { 
        \ShortCascade
          {\begin{tabular}{c}ganz rational, Polynom:\\ $y=(x)=x$\end{tabular}}
          {\begin{tabular}{c}gebrochen rational:\\ $y=f(x)=\frac{1}{x}$\end{tabular}}
        rational
      }
      {}
      {\begin{tabular}{c}irrational\\ $y=f(x)=\sqrt{x}$\end{tabular}}
    algebraisch
  }
  {}
  {\begin{tabular}{c}tranzendent\\ $y=f(x)=\sin x$\end{tabular}}
elemantar

\bigskip

\Cascade
  { 
    \Cascade
      { 
        \ShortCascade
          {\begin{tabular}{c}ganz rational, Polynom:\\ $y=(x)=x$\end{tabular}}
          {\begin{tabular}{c}gebrochen rational:\\ $y=f(x)=\frac{1}{x}$\end{tabular}}
        rational
      }
      {}
      {}
      {\begin{tabular}{c}irrational\\ $y=f(x)=\sqrt{x}$\end{tabular}}
    algebraisch
  }
  {}
  {}
  {\begin{tabular}{c}tranzendent\\ $y=f(x)=\sin x$\end{tabular}}
elemantar

\vspace{1cm}

\Cascade
  {}
  {
    \Cascade
      {}
      { 
        \ShortCascade
          {\begin{tabular}{c}ganz rational, Polynom:\\ $y=(x)=x$\end{tabular}}
          {\begin{tabular}{c}gebrochen rational:\\ $y=f(x)=\frac{1}{x}$\end{tabular}}
        \makebox[\widthof{$y=f(x)=\sqrt{x}$}]{rational}
      }
      {}
      {\begin{tabular}{c}irrational\\ $y=f(x)=\sqrt{x}$\end{tabular}}
    \makebox[\widthof{$y=f(x)=\sin(x)$}]{algebraisch}
  }
  {}
  {\begin{tabular}{c}tranzendent\\ $y=f(x)=\sin x$\end{tabular}}
elemantar

\bigskip

\Cascade
  { 
    \Cascade
      { 
        \ShortCascade
          {\begin{tabular}{c}ganz rational, Polynom:\\ $y=(x)=x$\end{tabular}}
          {\begin{tabular}{c}gebrochen rational:\\ $y=f(x)=\frac{1}{x}$\end{tabular}}
        \makebox[\widthof{$y=f(x)=\sqrt{x}$}]{rational}
      }
      {}
      {}
      {\begin{tabular}{c}irrational\\ $y=f(x)=\sqrt{x}$\end{tabular}}
    \makebox[\widthof{$y=f(x)=\sin(x)$}]{algebraisch}
  }
  {}
  {}
  {\begin{tabular}{c}tranzendent\\ $y=f(x)=\sin x$\end{tabular}}
elemantar

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Left aligning and breaking equations in cases environment

Nested right cases

Related Question