This issue occurs because the "anfis" function does not guarantee convergence for membership functions since each membership function has specific parameter constraints.
The "Neuro-Fuzzy Designer" app utilizes the same "anfis" function as mentioned in your code above, thus we get the same error message:
Error using fuzzy.internal.utility/validateTriMFParameterValuesFirst parameter must be less than or equal to second parameter.
A potential workaround is to change the value of "triOpt.InitialStepSize" to 0.001 from 0.01 in the code provided. This will result in the "anfis" function taking smaller steps thus reducing the probability of choosing invalid membership function parameters.
Another workaround is to use the "tunefis" function to tune the Fuzzy Inference System instead of "anfis". This can be achieved by replacing the following line of code:
[triFis,triTrErr,~,triChkFis,triCkErr] = anfis(tr_data,triOpt);
with the lines of code below:
[in,out,rule] = getTunableSettings(triAnfis);
tunefis(triAnfis,rule,inputData,outputData,tunefisOptions("Method","tune_method"));
"getTunableSettings" will provide parameters that are required for the "tunefis" function. The "tunefis" function will then tune the Fuzzy Inference System using the tuning method mentioned in "tunefisOptions". "tunefisOptions" has the following methods to choose from:
- "ga" — genetic algorithm
- "particleswarm" — particle swarm
- "patternsearch" — pattern search
- "simulannealbnd" — simulated annealing algorithm
This will allow you to tune the Fuzzy Inference System using alternative methods to "anfis".
For more information on "getTunableSettings", "tunefis" and "tunefisOptions", please refer to the documentation below:
"getTunableSettings" - https://www.mathworks.com/help/releases/R2022b/fuzzy/mamfis.gettunablesettings.html
"tunefis" - https://www.mathworks.com/help/releases/R2022b/fuzzy/tunefis.html
"tunefisOptions" - https://www.mathworks.com/help/releases/R2022b/fuzzy/tunefisoptions.html
