fismf

Fuzzy membership function

Description

Use a fismf object to represent a type-1 fuzzy membership function. For each input and output variable in a fuzzy inference system (FIS), one or more membership functions define the possible linguistic sets for that variable. For more information on membership functions, see Foundations of Fuzzy Logic.

Creation

Syntax

mf = fismf

mf = fismf(type,parameters)

mf = fismf('Name',name)

mf = fismf(type,parameters,"Name",name)

Description

mf = fismf creates a fuzzy membership function (MF) with default type, parameters, and name. To change the membership function properties, use dot notation.

mf = fismf(type,parameters) sets the Type and Parameters properties.

mf = fismf('Name',name) sets the Name property.

mf = fismf(type,parameters,"Name",name) sets the Type, Parameters, and Name properties.

Properties

Name — Membership function name

"mf" (default) | string | character vector

Membership function name, specified as a string or character vector.

Type — Membership function type

"trimf" (default) | string | character vector | function handle

Membership function type, specified as a string or character vector that contains the name of a function in the current working folder or on the MATLAB^® path. You can also specify a handle to such a function. When you specify Type, you must also specify Parameters.

This table describes the values that you can specify for Type.

Membership Function Type	Description	For More Information
"gbellmf"	Generalized bell-shaped membership function	gbellmf
"gaussmf"	Gaussian membership function	gaussmf
"gauss2mf"	Gaussian combination membership function	gauss2mf
"trimf"	Triangular membership function	trimf
"trapmf"	Trapezoidal membership function	trapmf
"linsmf"	Linear s-shaped saturation membership function (since R2022a)	linsmf
"linzmf"	Linear z-shaped saturation membership function (since R2022a)	linzmf
"sigmf"	Sigmoidal membership function	sigmf
"dsigmf"	Difference between two sigmoidal membership functions	dsigmf
"psigmf"	Product of two sigmoidal membership functions	psigmf
"zmf"	Z-shaped membership function	zmf
"pimf"	Pi-shaped membership function	pimf
"smf"	S-shaped membership function	smf
"constant"	Constant membership function for Sugeno output membership functions	Sugeno Fuzzy Inference Systems
"linear"	Linear membership function for Sugeno output membership functions
String or character vector	Name of a custom membership function in the current working folder or on the MATLAB path. Custom output membership functions are not supported for Sugeno systems.	Build Fuzzy Systems Using Custom Functions
Function handle	Handle to a custom membership function in the current working folder or on the MATLAB path. Custom output membership functions are not supported for Sugeno systems.

Note

When you change Type using dot notation, the values in Parameters are automatically converted for the new membership function type.

Parameters — Membership function parameters

[0 0.5 1] (default) | vector

Membership function parameters, specified as a vector. The length of the parameter vector depends on the membership function type. When you specify Parameters, you must also specify Type.

Object Functions

evalmf

Evaluate fuzzy membership function

Examples

Create Membership Function

Create fuzzy membership function with default settings.

mf = fismf;

To modify the membership function settings, use dot notation. For example, specify a Gaussian membership function with a standard deviation of 2 and a mean of 10.

mf.Type = "gaussmf";
mf.Parameters = [2 10];

Create Membership Function with Specified Parameters

Create a trapezoidal membership function with specified parameters.

mf = fismf("trapmf",[10 15 20 25]);

Create Membership Function with Specified Name

Create a membership function with the name "large".

mf = fismf("Name","large");

Version History

Introduced in R2018b