# How to make a multi-definition inside table

I have a function with multi-definition And I want to take it into a table. But i don't know how do that. Please help me, the image below is the result I want to have.

I used booktabs to have a better looking table; in particular, no use of vertical rules; the definitions by cases were built using the cases environment from amsmath:

\documentclass{article}
\usepackage{booktabs}
\usepackage{amsmath}
\usepackage{array}

\begin{document}

\noindent\begin{tabular}{c>{$}c<{$}>{$}c<{$}}
\toprule
Function & \multicolumn{1}{c}{Definition} & \multicolumn{1}{c}{Range} \\
\midrule
Linear & f(x)=x & (-\infty,\infty) \\[2ex]
Symmetric Saturating Linear & f(x)=\begin{cases}-1, &\quad x<1. \\ x, &\quad -1\leq x\leq 1 \\ 1, &\quad x>1.\end{cases} & [-1,1] \\[5ex]
Log-Sygmoid & f(x) = \dfrac{1}{1+e^{-x}} & (0,1) \\[3ex]
Hyperbolic Tangent Sygmoid & f(x) = \dfrac{e^{x}-e^{-x}}{e^{x}+e^{-x}} & (-1,1) \\[3ex]
Hard Limit & f(x)=\begin{cases}0, &\quad x<0. \\ 1, &\quad x\geq 1. \end{cases} & \{0,1 \} \\
\bottomrule
\end{tabular}

\end{document}


Another option, with a different alignment in the first cases:

\documentclass{article}
\usepackage{booktabs}
\usepackage{amsmath}
\usepackage{array}

\begin{document}

\noindent\begin{tabular}{c>{$}c<{$}>{$}c<{$}}
\toprule
Function & \multicolumn{1}{c}{Definition} & \multicolumn{1}{c}{Range} \\
\midrule
Linear & f(x)=x & (-\infty,\infty) \\[2ex]
Symmetric Saturating Linear & f(x)=\begin{cases}-1, &\quad\hfill x<1. \\ \phantom{-}x, &\quad -1\leq x\leq 1. \\ \phantom{-}1, &\quad\hfill x>1.\end{cases} & [-1,1] \\[5ex]
Log-Sygmoid & f(x) = \dfrac{1}{1+e^{-x}} & (0,1) \\[3ex]
Hyperbolic Tangent Sygmoid & f(x) = \dfrac{e^{x}-e^{-x}}{e^{x}+e^{-x}} & (-1,1) \\[3ex]
Hard Limit & f(x)=\begin{cases}0, &\quad x<0. \\ 1, &\quad x\geq 1. \end{cases} & \{0,1 \} \\
\bottomrule
\end{tabular}

\end{document}


In case the original vertical rules are required, you're table would look like:

\documentclass{article}
\usepackage{amsmath}
\usepackage{array}

\begin{document}

\noindent\begin{tabular}{|| l | >{$}c<{$} | >{$}c<{$} ||}
\hline
Function & \multicolumn{1}{c|}{Definition} & \multicolumn{1}{c||}{Range} \\
\hline
Linear & f(x)=x & (-\infty,\infty) \\[1ex]
Symmetric Saturating Linear & f(x)=\begin{cases}-1, &\quad x<1. \\ x, &\quad -1\leq x\leq 1 \\ 1, &\quad x>1.\end{cases} & [-1,1] \\
\hline
\end{tabular}

\end{document}