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enter image description hereI have the following equation:

‎‎

\begin{equation*}‎
    \left\{‎ 
    ‎\begin{array}{lll}‎
    ‎-\mathrm{f}-2,‎ ‎& z_{\left( \mathrm{f}+i\right) \left( j_{1},j_{2}\right) }=-1‎, ‎&‎ 
    ‎S_{\mathbf{z}_{\left( j_{1},j_{2},i\right) }}^{1\-- \mathrm{f}}=-1‎, ‎\\‎ 
    ‎\text{ \ }\mathrm{f}‎, ‎& z_{\left( \mathrm{f}+i\right) \left( j_{1},j_{2}\right) }=+1‎, ‎&‎ 
    ‎S_{\mathbf{z}_{\left( j_{1},j_{2},i\right) }}^{1\-- \mathrm{f}}=-1‎, ‎\\‎ 
    ‎-\mathrm{f}+6,‎ ‎& z_{\left( \mathrm{f}+i\right) \left( j_{1},j_{2}\right) }=-1‎, ‎&‎ 
    ‎S_{\mathbf{z}_{\left( j_{1},j_{2},i\right) }}^{1\-- \mathrm{f}}=\text{ \‎ }%
    ‎7‎, ‎\\‎ 
    ‎\text{ \ }\mathrm{f}+8‎, ‎& z_{\left( \mathrm{f}+i\right) \left( j_{1},j_{2}\right) }=+1‎, ‎&‎ 
    ‎S_{\mathbf{z}_{\left( j_{1},j_{2},i\right) }}^{1\-- \mathrm{f}}=\text{ \‎ }%
    ‎7,%‎
    ‎\end{array}%‎
    ‎‎\end{equation*}%

how can I increase the space between rows of this array without use \\‎‎ ?

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  • array is intended for arrays and matrices not for a multi-line display , you could use \arraystretch but better would be to use a cases environment from amsmath Commented Dec 6, 2016 at 12:48

1 Answer 1

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I wouldn't bother fine-tuning the settings of the array environment. Instead, I would use the dedicated dcases environment, provided by the mathtools package, as it is tailor-made for situations such as yours. (The "d" in "dcases" stands for "display style" math mode.)

Observe the use of several \phantom statements to adjust some of the character positions. I've also gotten rid of all \left and \right modifiers since they do nothing except provide code clutter.

enter image description here

\documentclass{article}
\usepackage{mathtools} % for "dcases" environment
\begin{document}

\begin{equation*}‎
‎\begin{dcases}‎
    ‎{-}\mathrm{f}-2,‎ 
    ‎& z_{( \mathrm{f}+i) ( j_{1},j_{2}) }=-1‎, ‎\quad‎
    ‎S_{\mathbf{z}_{(j_{1},j_{2},i) }}^{1-\mathrm{f}}=-1‎, ‎\\‎
    \phantom{‎-}\mathrm{f}\phantom{{}-2}‎, ‎
    & z_{( \mathrm{f}+i) ( j_{1},j_{2}) } =+1‎, \quad‎
    ‎S_{\mathbf{z}_{(j_{1},j_{2},i) }}^{1-\mathrm{f}}=-1‎, ‎\\‎
    ‎{-}\mathrm{f}+6,‎ 
    ‎& z_{( \mathrm{f}+i) ( j_{1},j_{2}) }=-1‎, ‎\quad
    ‎S_{\mathbf{z}_{(j_{1},j_{2},i) }}^{1-\mathrm{f}}= \phantom{-}7‎, ‎\\‎
    \phantom{‎-}\mathrm{f}+8‎,
    ‎& z_{( \mathrm{f}+i) ( j_{1},j_{2}) }=+1‎, ‎\quad
    ‎S_{\mathbf{z}_{(j_{1},j_{2},i) }}^{1-\mathrm{f}}= \phantom{-}‎7,‎
\end{dcases} 
\end{equation*}
\end{document}
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  • How can I use dcases in the following equation? \begin{equation*}‎ ‎\begin{array}{ll}‎ ‎\chi \left(‎ -‎1\right) =-1‎, ‎& \mathrm{f} =3‎, ‎\\‎ ‎\chi \left(‎ -‎1\right) =+1‎, ‎& \mathrm{f} =1,%‎ ‎\end{array}%‎ ‎\end{equation*}
    – Fahim B
    Commented Dec 6, 2016 at 14:17
  • @FahimB - Piece of cake: \begin{equation*}‎ ‎\begin{dcases}‎ ‎\chi(-‎1)=-1‎, ‎& \mathrm{f}=3‎; ‎\\‎ ‎\chi(-‎1)=+1‎, ‎& \mathrm{f}=1. ‎\end{dcases}‎ ‎\end{equation*}. Oh, and for sanity's sake, please cease using \left and \right in front of each and every parenthesis. It's simply not correct usage! Who taught you this bad habit?! Please unlearn it.
    – Mico
    Commented Dec 6, 2016 at 15:00
  • @micro Thank you very much. I wrote this text first by scientific workplace and these \left and \right are from that software. I hope to ride this habit. Is it possible to ride { from the left of decases?
    – Fahim B
    Commented Dec 6, 2016 at 15:48
  • @FahimB - my userid is Mico, not Micro.
    – Mico
    Commented Dec 6, 2016 at 17:36

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