bugGNU Octave - Bugs: bug #56008, [octave forge]...

 
 

bug #56008: [octave forge] (fuzzy-logic-toolkit) defuzz provides inaccurate result

Submitted by:  Luis <lalucas_1967>
Submitted on:  Wed 27 Mar 2019 02:18:05 PM UTC  
 
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Inaccurate Result
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  Open
Release:  dev Operating System:  GNU/Linux

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Wed 27 Mar 2019 02:42:45 PM UTC, comment #1:

As a general answer, not a specific answer ( I don't know why it was done this way). Fuzzy controllers are nonlinear controllers usually controlling nonlinear processes, and in practice this approximate method works just fine. Years ago we did not have as powerful CPUs and therefor the faster approximations were used. Try implementing a fuzzy controller in a microcontroller and you fill see that the faster method is desirable.
But like I said at the beginning, it is all non linear and perfect accuracy is not needed.    

Doug Stewart <dastew>
Wed 27 Mar 2019 02:18:05 PM UTC, original submission:

Why did you implement defuzz with an approximated approach (by means of the trapz integral) if an exact approach exist?

Consider the following example:

X=[3;4;5];
params=[1 4.5 5 6];
Y=trapmf(X,params);
defuzz(X,Y,'centroid')

which provides 4.1304, but the exact result is

X'*Y/sum(Y)

which is 4.1765.

Luis <lalucas_1967>

 

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-03-27 mtmiller Release5.1.0 => dev
        Summarydefuzz provides inaccurate result => [octave forge] (fuzzy-logic-toolkit) defuzz provides inaccurate result

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