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/*
fuzzylite (R), a fuzzy logic control library in C++.
Copyright (C) 2010-2017 FuzzyLite Limited. All rights reserved.
Author: Juan Rada-Vilela, Ph.D. <jcrada@fuzzylite.com>
This file is part of fuzzylite.
fuzzylite is free software: you can redistribute it and/or modify it under
the terms of the FuzzyLite License included with the software.
You should have received a copy of the FuzzyLite License along with
fuzzylite. If not, see <http://www.fuzzylite.com/license/>.
fuzzylite is a registered trademark of FuzzyLite Limited.
*/
#ifndef FL_SIGMOID_H
#define FL_SIGMOID_H
#include "fl/term/Term.h"
namespace fl {
/**
The Sigmoid class is an edge Term that represents the sigmoid membership
function.
@image html sigmoid.svg
@author Juan Rada-Vilela, Ph.D.
@see Term
@see Variable
@since 4.0
*/
class FL_API Sigmoid : public Term {
private:
scalar _inflection;
scalar _slope;
public:
/**
Direction is an enumerator that indicates the direction of the
sigmoid.
*/
enum Direction {
/** `(_/)` increases to the right */ Positive,
/** `(--)` slope is zero */ Zero,
/** `(\\_)` increases to the left */ Negative
};
explicit Sigmoid(const std::string& name = "",
scalar inflection = fl::nan,
scalar slope = fl::nan,
scalar height = 1.0);
virtual ~Sigmoid() FL_IOVERRIDE;
FL_DEFAULT_COPY_AND_MOVE(Sigmoid)
virtual std::string className() const FL_IOVERRIDE;
/**
Returns the parameters of the term
@return `"inflection slope [height]"`
*/
virtual std::string parameters() const FL_IOVERRIDE;
/**
Configures the term with the parameters
@param parameters as `"inflection slope [height]"`
*/
virtual void configure(const std::string& parameters) FL_IOVERRIDE;
virtual Complexity complexity() const FL_IOVERRIDE;
/**
Computes the membership function evaluated at @f$x@f$
@param x
@return @f$ h / (1 + \exp(-s(x-i)))@f$
where @f$h@f$ is the height of the Term,
@f$s@f$ is the slope of the Sigmoid,
@f$i@f$ is the inflection of the Sigmoid
*/
virtual scalar membership(scalar x) const FL_IOVERRIDE;
virtual scalar tsukamoto(scalar activationDegree,
scalar minimum, scalar maximum) const FL_IOVERRIDE;
virtual bool isMonotonic() const FL_IOVERRIDE;
/**
Sets the inflection of the sigmoid
@param inflection is the inflection of the sigmoid
*/
virtual void setInflection(scalar inflection);
/**
Gets the inflection of the sigmoid
@return the inflection of the sigmoid
*/
virtual scalar getInflection() const;
/**
Sets the slope of the sigmoid
@param slope is the slope of the sigmoid
*/
virtual void setSlope(scalar slope);
/**
Gets the slope of the sigmoid
@return the slope of the sigmoid
*/
virtual scalar getSlope() const;
/**
Returns the direction of the sigmoid
@return the direction of the sigmoid
*/
virtual Direction direction() const;
virtual Sigmoid* clone() const FL_IOVERRIDE;
static Term* constructor();
};
}
#endif /* FL_SIGMOID_H */
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