public static double sigmoid(double x) {
    if (x<0) {
      double num = Math.exp(x);
      return num / (1.0 + num);
    }
    else {
      double den = 1.0 + Math.exp(-x);
      return 1.0 / den;
    }
  }
public static double sigmoid ( double x ) { if ( x < 0 ) { double num = Math . exp ( x ) ; return num / ( 1.0 + num ) ; } else { double den = 1.0 + Math . exp ( - x ) ; return 1.0 / den ; } }
Compute the sigmoid function with mean zero.
Care is taken to compute an accurate answer without
numerical overflow. (Added by rajatr)

@param x Point to compute sigmoid at.
@return Value of the sigmoid, given by 1/(1+exp(-x))