Defining a Case Function in Mathematica: A Convenient Solution?

[omri3012]

Does anyone familiar with a convenient way in Mathematica to define a case function such as:

$y(x)=\left\{\begin{array}{c} x \\ -x\end{array}\begin{array}{c} x>0 \\ x<0\end{array}<br /> \right.$
?

Thankes,
Omri

 

[phyzguy]

You want to use 'Piecewise':

y[x_]:=Piecewise[{{x,x>0},{-x,x<0}}]

 

[omri3012]

Thankes,
It's very helpful :)