Class: QgsGenericNumericTransformer

class qgis.core.QgsGenericNumericTransformer

Bases: QgsPropertyTransformer

QgsPropertyTransformer subclass for scaling an input numeric value into an output numeric value.

New in version 3.0.

QgsGenericNumericTransformer(minValue: float = 0, maxValue: float = 1, minOutput: float = 0, maxOutput: float = 1, nullOutput: float = 0, exponent: float = 1) Constructor for QgsGenericNumericTransformer.

Parameters:
  • minValue – minimum expected input value

  • maxValue – maximum expected input value

  • minOutput – minimum value to return

  • maxOutput – maximum value to return

  • nullOutput – value to return for null inputs

  • exponent – optional exponential for non-linear scaling

QgsGenericNumericTransformer(QgsGenericNumericTransformer)

Methods

clone

rtype:

QgsGenericNumericTransformer

exponent

Returns the exponent for an exponential expression.

fromExpression

Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.

loadVariant

param definition:

maxOutputValue

Returns the maximum calculated size.

minOutputValue

Returns the minimum calculated size.

nullOutputValue

Returns the size value when an expression evaluates to NULL.

setExponent

Sets the exponent for an exponential expression.

setMaxOutputValue

Sets the maximum calculated size.

setMinOutputValue

Sets the minimum calculated size.

setNullOutputValue

Sets the size value for when an expression evaluates to NULL.

toExpression

param baseExpression:

toVariant

rtype:

Any

transform

param context:

transformNumeric

Applies base class numeric transformations.

transformerType

rtype:

QgsPropertyTransformer.Type

value

Calculates the size corresponding to a specific input value.

clone(self) QgsGenericNumericTransformer
Return type:

QgsGenericNumericTransformer

exponent(self) float

Returns the exponent for an exponential expression.

See also

setExponent()

Return type:

float

fromExpression(expression: str) Tuple[QgsGenericNumericTransformer, str, str]

Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.

Parameters:

expression (str) – expression to parse

Return type:

Tuple[QgsGenericNumericTransformer, str, str]

Returns:

  • corresponding QgsSizeScaleTransformer, or None if expression could not

  • baseExpression: will be set to the component of the source expression which is used to calculate the input to the property transformer. This will be set to an empty string if a field reference is the transformer input.

  • fieldName: will be set to a field name which is used to calculate the input to the property transformer. This will be set to an empty string if an expression is the transformer input.

be parsed to a size scale transformer.

loadVariant(self, definition: Any) bool
Parameters:

definition (Any) –

Return type:

bool

maxOutputValue(self) float

Returns the maximum calculated size.

See also

minOutputValue()

Return type:

float

minOutputValue(self) float

Returns the minimum calculated size.

See also

maxOutputValue()

Return type:

float

nullOutputValue(self) float

Returns the size value when an expression evaluates to NULL.

Return type:

float

setExponent(self, exponent: float)

Sets the exponent for an exponential expression.

Parameters:

exponent (float) – exponent

See also

exponent()

setMaxOutputValue(self, size: float)

Sets the maximum calculated size.

Parameters:

size (float) – maximum size

See also

maxOutputValue()

setMinOutputValue(self, size: float)

Sets the minimum calculated size.

Parameters:

size (float) – minimum size

See also

minOutputValue()

setNullOutputValue(self, size: float)

Sets the size value for when an expression evaluates to NULL.

Parameters:

size (float) – null size

toExpression(self, baseExpression: str) str
Parameters:

baseExpression (str) –

Return type:

str

toVariant(self) Any
Return type:

Any

transform(self, context: QgsExpressionContext, value: Any) Any
Parameters:
Return type:

Any

transformNumeric(self, input: float) float

Applies base class numeric transformations. Derived classes should call this to transform an input numeric value before they apply any transform to the result. This applies any curve transforms which may exist on the transformer.

transformerType(self) QgsPropertyTransformer.Type
Return type:

QgsPropertyTransformer.Type

value(self, input: float) float

Calculates the size corresponding to a specific input value.

Return type:

float

Returns:

calculated size using size scale transformer’s parameters and type

Parameters:

input (float) –