Determines the abscissa of the reference point of a fuzzy set and the
membership value corresponding to it.
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Parameters
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mftype - the type of the fuzzy set.
Implemeted types are: 'singlmf','trimf','trapmf'
params - the first array of parameters that defines the shape of the set.
Ususally it contains the abscissas of the characteristic points
of the shape.
paramsy - the second array of parameters that defines the shape of the set.
Ususally it contains the ordinates of the characteristic points
of the shape.
rptype - the type of the reference point
implemeted types are: 'corecentre','corecentreprojection'
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Returned values
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RPx - the abscissa of the reference point
RPy - the membership value of the reference point
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Zsolt Csaba Johanyák, johanyak.csaba@gamf.kefo.hu, v. 2.3, 25. October 2006.