plotmf

Plot membership functions for input or output variable

Syntax

plotmf(fis,variableType,variableIndex)

plotmf(___,numPoints)

[xOut,mfOut] = plotmf(___)

[xOut,umfOut,lmfOut] = plotmf(___)

Description

plotmf(fis,variableType,variableIndex) plots the membership functions for an input or output variable in the fuzzy inference system fis.

plotmf(___,numPoints) specifies the number of data points to plot for each membership function.

[xOut,mfOut] = plotmf(___) returns the universe of discourse (xOut) and membership function (mfOut) values without plotting them. Use this syntax when fis is a type-1 fuzzy inference system.

[xOut,umfOut,lmfOut] = plotmf(___) returns the universe of discourse (xOut), upper membership function (umfOut), and lower membership function (lmfOut) values without plotting them. Use this syntax when fis is a type-2 fuzzy inference system.

Examples

Plot Membership Functions for Input Variable

Create a fuzzy inference system.

fis = readfis('tipper');

Plot the membership functions for the first input variable.

plotmf(fis,'input',1)

Specify Number of Points for Membership Function Plot

Create a fuzzy inference system.

fis = readfis('tipper');

Plot the membership functions for the first output variable using 101 data points for each membership function.

plotmf(fis,'output',1,101)

Obtain Membership Function Plot Data

Create a fuzzy inference system.

fis = readfis('tipper');

Obtain the x-axis and y-axis data for the membership functions of the second input variable.

[xOut,yOut] = plotmf(fis,'input',2);

You can then, for example, plot a single membership function using this data.

plot(xOut(:,2),yOut(:,2))
xlabel('food')
ylabel('delicious membership')

Plot Membership Functions for Type-2 FIS

Create a type-2 fuzzy inference system.

fis = mamfistype2('NumInputs',3,'NumOutputs',1);

Plot the membership functions for the second input variable.

plotmf(fis,'input',1)

The type-2 membership functions have a footprint of uncertainty (FOU) between their upper and lower membership functions.

You can also obtain the plotting data without generating a plot.

[xOut,umfOut,lmfOut] = plotmf(fis,'input',1);

You can then plot individual membership functions or plot the data using your own custom formatting. For example, plot the upper and lower membership functions for only the second membership function of the first input variable.

plot(xOut(:,2),umfOut(:,2),'r',xOut(:,2),lmfOut(:,2),'b')
xlabel('input1')
ylabel('delicious membership')

Input Arguments

fis — Fuzzy inference system

mamfis object | sugfis object | mamfistype2 object | sugfistype2 object

Fuzzy inference system, specified as one of the following:

• mamfis object — Mamdani fuzzy inference system

• sugfis object — Sugeno fuzzy inference system

• mamfistype2 object — Type-2 Mamdani fuzzy inference system

• sugfistype2 object — Type-2 Sugeno fuzzy inference system

plotmf does not support plotting output membership functions of Sugeno systems.

variableType — Variable type

'input' | 'output'

Variable type, specified as one of the following:

• 'input' — Input variable

• 'output' — Output variable

variableIndex — Variable index

positive integer

Variable index, specified as a positive integer. If variableType is:

• 'input', then variableIndex must be less than or equal to the number of input variables in fis

• 'output', then variableIndex must be less than or equal to the number of output variables in fis

numPoints — Number of data points to plot

181 (default) | positive integer

Number of data points to plot, specified as a positive integer.

Output Arguments

xOut — Universe of discourse data

array

Universe of discourse data, returned as a numPoints-by-N_MF array, where N_MF is the number of membership functions for the variable specified by variableType and variableIndex.

mfOut — Membership function data

array

Membership function data for a type-1 membership function, returned as a numPoints-by-N_MF array, where N_MF is the number of membership functions for the variable specified by variableType and variableIndex.

umfOut — Upper membership function data

array

Upper membership function data for a type-2 membership function, returned as a numPoints-by-N_MF array, where N_MF is the number of membership functions for the variable specified by variableType and variableIndex.

lmfOut — Lower membership function data

array

Lower membership function data for a type-2 membership function, returned as a numPoints-by-N_MF array, where N_MF is the number of membership functions for the variable specified by variableType and variableIndex.

Compatibility Considerations

Support for representing fuzzy inference systems as structures will be removed

Warns starting in R2019b

Support for representing fuzzy inference systems as structures will be removed in a future release. Use mamfis and sugfis objects instead. There are differences between these representations that require updates to your code. These differences include:

• Object property names that differ from the corresponding structure fields.

• Objects store text data as strings rather than as character vectors.

Also, all Fuzzy Logic Toolbox™ functions that accepted or returned fuzzy inference systems as structures now accept and return either mamfis or sugfis objects.

To convert existing fuzzy inference system structures to objects, use the convertfis function.