This information is part of the Business Simulation Library (BSL). Please support this work and ► donate.

The function returns the degree of membership using a sigmoid function function given the real input x and the parameters shape parameter to control width of transition area a and center of transition area c.

The sigmoid function will increase from 0 to 1 for positive values of a, while negative values will give rise to a z-shaped transition.

Implementation

y := 1 / (1 + exp(-a * (x - c)));

Syntax

Functions.sigmf(x, a, c);

Examples

Functions.sigmf( 4, a=2, c=4); // 0.5
Functions.sigmf( 2, a=2, c=4); // 0.0179862..
Functions.sigmf( 6, a=2, c=4); // 0.98201379..

See also

evalmf, rampmf, trimf, trapmf, smf, sigmf, pimf, psigmf, gaussmf, gbellmf

y = sigmf(x, a, c)

x	Type: Real Description: Input value for which the degree of membership is to be computed
a	Type: Real Description: Shape parameter controlling the width of s-shaped transition area (higher values → steeper transition)
c	Type: Real Description: Center of the s-shaped transition area

y	Type: Real Description: Degree of membership