1 files changed, 124 insertions, 0 deletions
diff --git a/fuzzylite/src/term/Sigmoid.cpp b/fuzzylite/src/term/Sigmoid.cpp
new file mode 100644
index 0000000..fcf165e
--- /dev/null
+++ b/fuzzylite/src/term/Sigmoid.cpp
@@ -0,0 +1,124 @@
+/*
+ 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.
+ */
+
+#include "fl/term/Sigmoid.h"
+
+namespace fl {
+
+    Sigmoid::Sigmoid(const std::string& name, scalar inflection, scalar slope, scalar height)
+    : Term(name, height), _inflection(inflection), _slope(slope) { }
+
+    Sigmoid::~Sigmoid() { }
+
+    std::string Sigmoid::className() const {
+        return "Sigmoid";
+    }
+
+    Complexity Sigmoid::complexity() const {
+        return Complexity().comparison(1).arithmetic(1 + 4).function(1);
+    }
+
+    scalar Sigmoid::membership(scalar x) const {
+        if (Op::isNaN(x)) return fl::nan;
+        return Term::_height * 1.0 / (1.0 + std::exp(-_slope * (x - _inflection)));
+    }
+
+    scalar Sigmoid::tsukamoto(scalar activationDegree,
+            scalar minimum, scalar maximum) const {
+
+        scalar w = activationDegree;
+        scalar z = fl::nan;
+
+        if (Op::isEq(w, 1.0)) {
+            if (Op::isGE(_slope, 0.0)) {
+                z = maximum;
+            } else {
+                z = minimum;
+            }
+
+        } else if (Op::isEq(w, 0.0)) {
+            if (Op::isGE(_slope, 0.0)) {
+                z = minimum;
+            } else {
+                z = maximum;
+            }
+        } else {
+            scalar a = _slope;
+            scalar b = _inflection;
+            z = b + (std::log(1.0 / w - 1.0) / -a);
+        }
+
+        return z;
+    }
+
+    bool Sigmoid::isMonotonic() const {
+        return true;
+    }
+
+    std::string Sigmoid::parameters() const {
+        return Op::join(2, " ", _inflection, _slope) +
+                (not Op::isEq(getHeight(), 1.0) ? " " + Op::str(getHeight()) : "");
+    }
+
+    void Sigmoid::configure(const std::string& parameters) {
+        if (parameters.empty()) return;
+        std::vector<std::string> values = Op::split(parameters, " ");
+        std::size_t required = 2;
+        if (values.size() < required) {
+            std::ostringstream ex;
+            ex << "[configuration error] term <" << className() << ">"
+                    << " requires <" << required << "> parameters";
+            throw Exception(ex.str(), FL_AT);
+        }
+        setInflection(Op::toScalar(values.at(0)));
+        setSlope(Op::toScalar(values.at(1)));
+        if (values.size() > required)
+            setHeight(Op::toScalar(values.at(required)));
+    }
+
+    void Sigmoid::setSlope(scalar a) {
+        this->_slope = a;
+    }
+
+    scalar Sigmoid::getSlope() const {
+        return this->_slope;
+    }
+
+    void Sigmoid::setInflection(scalar c) {
+        this->_inflection = c;
+    }
+
+    scalar Sigmoid::getInflection() const {
+        return this->_inflection;
+    }
+
+    Sigmoid::Direction Sigmoid::direction() const {
+        if (not Op::isFinite(_slope) or Op::isEq(_slope, 0.0)) return Zero;
+
+        if (Op::isGt(_slope, 0.0)) return Positive;
+
+        return Negative;
+    }
+
+    Sigmoid* Sigmoid::clone() const {
+        return new Sigmoid(*this);
+    }
+
+    Term* Sigmoid::constructor() {
+        return new Sigmoid;
+    }
+
+}