Example

> sign(3)
        1  
> sign(-3)
       -1  
> sign(0)
        0  
> sign(3+4j)
      0.6 + 0.8i
> a = (rand(2,5)-0.5)*10
 a =
        5       1.47      -4.63       1.65      -2.96  
     4.75      -1.67      -3.38      -4.15      -3.33  
> sign(a)
        1          1         -1          1         -1  
        1         -1         -1         -1         -1