increasing space between rows of an array

Question

I 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 \\‎‎ ?

Answer 1

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.

\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}