Variable

InputVariable

Bases: Variable

Variable to represent the input of a fuzzy logic controller.

related

• fuzzylite.variable.Variable
• fuzzylite.variable.OutputVariable
• fuzzylite.term.Term

Functions

__init__

__init__(
    name: str = "",
    description: str = "",
    enabled: bool = True,
    minimum: float = -inf,
    maximum: float = inf,
    lock_range: bool = False,
    terms: Iterable[Term] | None = None,
) -> None

Constructor.

Parameters:

Name	Type	Description	Default
name	str	name of the variable	''
description	str	description of the variable	''
enabled	bool	enable the variable	True
minimum	float	minimum value of the variable	-inf
maximum	float	maximum value of the variable	inf
lock_range	bool	lock the value to the range of the variable	False
terms	Iterable[Term] | None	list of terms.	None

__str__

__str__() -> str

Return the code to construct the input variable in the FuzzyLite Language.

Returns:

Type	Description
str	code to construct the input variable in the FuzzyLite Language.

fuzzy_value

fuzzy_value() -> Array[str_]

Return the current fuzzy input value.

The fuzzy value is computed by evaluating the membership function of the current input value \(x\) for each term \(i\), resulting in a fuzzy input value in the form \(\tilde{x}=\sum_i{\mu_i(x)/i}\).

Returns:

Type	Description
Array[str_]	current fuzzy value expressed as \(\sum_i{\mu_i(x)/i}\).

OutputVariable

Bases: Variable

Variable to represents the output of a fuzzy logic controller.

During the activation of a rule block, the activated terms of each rule are aggregated in the fuzzy output, which represents a fuzzy set hereinafter referred to as \(\tilde{y}\).

The defuzzification of \(\tilde{y}\) converts the fuzzy output value \(\tilde{y}\) into a crisp output value \(y\), which is stored as the value of this variable.

related

• fuzzylite.variable.Variable
• fuzzylite.variable.InputVariable
• fuzzylite.term.Term
• fuzzylite.rule.RuleBlock
• fuzzylite.norm.SNorm

Attributes

aggregation property writable

aggregation: SNorm | None

Get/Set the aggregation operator.

Getter

Returns:

Type	Description
SNorm | None	aggregation operator.

Setter

Parameters:

Name	Type	Description	Default
value	SNorm	aggregation operator	required

default_value instance-attribute

default_value = default_value

defuzzifier instance-attribute

defuzzifier = defuzzifier

fuzzy instance-attribute

fuzzy = Aggregated(name=name, minimum=minimum, maximum=maximum, aggregation=aggregation)

lock_previous instance-attribute

lock_previous = lock_previous

maximum property writable

maximum: float

Get/Set the maximum value of the range of the output variable.

Getter

Returns:

Type	Description
float	maximum value of the range of the output variable.

Setter

Parameters:

Name	Type	Description	Default
value	float	maximum value of the output variable.	required

minimum property writable

minimum: float

Get/Set the minimum value of the range of the output variable.

Getter

Returns:

Type	Description
float	minimum value of the range of the output variable.

Setter

Parameters:

Name	Type	Description	Default
value	float	minimum value of the output variable.	required

previous_value instance-attribute

previous_value = nan

Functions

__init__

__init__(
    name: str = "",
    description: str = "",
    enabled: bool = True,
    minimum: float = -inf,
    maximum: float = inf,
    lock_range: bool = False,
    lock_previous: bool = False,
    default_value: float = nan,
    aggregation: SNorm | None = None,
    defuzzifier: Defuzzifier | None = None,
    terms: Iterable[Term] | None = None,
) -> None

Constructor.

Parameters:

Name	Type	Description	Default
name	str	name of the variable	''
description	str	description of the variable	''
enabled	bool	enable the variable	True
minimum	float	minimum value of the variable	-inf
maximum	float	maximum value of the variable	inf
lock_range	bool	lock the value to the range of the variable	False
lock_previous	bool	lock the previous value of the output variable	False
default_value	float	default value of the output variable	nan
aggregation	SNorm | None	aggregation operator	None
defuzzifier	Defuzzifier | None	defuzzifier of the output variable	None
terms	Iterable[Term] | None	list of terms.	None

__repr__

__repr__() -> str

Return the code to construct the output variable in Python.

Returns:

Type	Description
str	code to construct the output variable in Python.

__str__

__str__() -> str

Return the code to construct the output variable in the FuzzyLite Language.

Returns:

Type	Description
str	code to construct the output variable in the FuzzyLite Language.

clear

clear() -> None

Clear the output variable.

defuzzify

defuzzify() -> None

Defuzzify the output variable and store the output value and the previous output value.

The final value \(y\) depends on the following cascade of properties in order of precedence expressed in the FuzzyLite Language:

• lock-previous: boolean: when the output value is not finite (ie, nan or inf) and lock-previous: true, then the output value is replaced with the value defuzzified in the previous iteration.

• default: scalar: when the output value is (still) not finite and the default value is not nan, then the output value is replaced with the default value.

• lock-range: boolean: when lock-range: true, the output value is clipped to the range of the variable.

fuzzy_value

fuzzy_value() -> Array[str_]

Return the current fuzzy output value.

Returns:

Type	Description
Array[str_]	current fuzzy output value.

Variable

Base class for linguistic variables.

related

• fuzzylite.variable.InputVariable
• fuzzylite.variable.OutputVariable

Attributes

description instance-attribute

description = description

drange property

drange: float

Return the magnitude of the range of the variable.

Returns:

Type	Description
float	maximum - minimum

enabled instance-attribute

enabled = enabled

lock_range instance-attribute

lock_range = lock_range

maximum instance-attribute

maximum = maximum

minimum instance-attribute

minimum = minimum

name instance-attribute

name = name

range property writable

range: tuple[float, float]

Return the range of the variable.

Getter

Returns:

Type	Description
tuple[float, float]	tuple of (minimum, maximum).

Setter

Parameters:

Name	Type	Description	Default
min_max	tuple[float, float]	range of the variable	required

terms instance-attribute

terms = list(terms or [])

value property writable

value: Scalar

Get/Set the value of the variable.

Getter

Returns:

Type	Description
Scalar	value of the variable

Setter

when lock_range = true, the value is clipped to the range of the variable

Parameters:

Name	Type	Description	Default
value	Scalar	value of the variable	required

Functions

__getitem__

__getitem__(item: int | str) -> Term

__getitem__(item: slice) -> list[Term]

__getitem__(item: int | str | slice) -> Term | list[Term]

Allow indexing terms by index, name, or slices (eg, engine["power"]["low"]).

Parameters:

Name	Type	Description	Default
item	int | str | slice	index, name, or slice of terms	required

Returns:

Type	Description
Term | list[Term]	term by index or name, or slice of terms

__init__

__init__(
    name: str = "",
    description: str = "",
    enabled: bool = True,
    minimum: float = -inf,
    maximum: float = inf,
    lock_range: bool = False,
    terms: Iterable[Term] | None = None,
) -> None

Constructor.

Parameters:

Name	Type	Description	Default
name	str	name of the variable	''
description	str	description of the variable	''
enabled	bool	enable the variable	True
minimum	float	minimum value of the range	-inf
maximum	float	maximum value of the range	inf
lock_range	bool	lock the value to the range of the variable	False
terms	Iterable[Term] | None	list of terms	None

__iter__

__iter__() -> Iterator[Term]

Return the iterator of the terms.

Returns:

Type	Description
Iterator[Term]	iterator of the terms

__len__

__len__() -> int

Return the number of terms.

Returns:

Type	Description
int	number of terms

__repr__

__repr__() -> str

Return the code to construct the variable in Python.

Returns:

Type	Description
str	code to construct the variable in Python.

__str__

__str__() -> str

Return the code to construct the variable in the FuzzyLite Language.

Returns:

Type	Description
str	code to construct the variable in the FuzzyLite Language.

clear

clear() -> None

Clear the variable to its initial state.

fuzzify

fuzzify(x: Scalar) -> Array[str_]

Return the fuzzy representation of \(x\).

The fuzzy representation is computed by evaluating the membership function of \(x\) for each term \(i\), resulting in a fuzzy value in the form \(\tilde{x}=\sum_i{\mu_i(x)/i}\)

Parameters:

Name	Type	Description	Default
x	Scalar	value to fuzzify	required

Returns:

Type	Description
Array[str_]	fuzzy value expressed as \(\sum_i{\mu_i(x)/i}\).

highest_membership

highest_membership(x: float) -> Activated | None

Return the term that has the highest membership function value for \(x\).

Parameters:

Name	Type	Description	Default
x	float	value	required

Returns:

Type	Description
Activated | None	term \(i\) that maximimizes \(\mu_i(x)\)

term

term(name_or_index: str | int) -> Term

Find the term by the name or index.

The best performance is \(O(1)\) when using indices, and the worst performance is \(O(n)\) when using names, where \(n\) is the number terms.

Parameters:

Name	Type	Description	Default
name_or_index	str | int	name or index of the term	required

Returns:

Type	Description
Term	term by the name or index

Raises:

Type	Description
ValueError	when there is no term by the given name.
IndexError	when the index is out of range