colour.Extrapolator

class colour.Extrapolator(interpolator=None, method='Linear', left=None, right=None, dtype=None)[source]

Bases: object

Extrapolates the 1-D function of given interpolator.

The colour.Extrapolator class acts as a wrapper around a given Colour or scipy interpolator class instance with compatible signature. Two extrapolation methods are available:

  • Linear: Linearly extrapolates given points using the slope defined by the interpolator boundaries (xi[0], xi[1]) if x < xi[0] and (xi[-1], xi[-2]) if x > xi[-1].

  • Constant: Extrapolates given points by assigning the interpolator boundaries values xi[0] if x < xi[0] and xi[-1] if x > xi[-1].

Specifying the left and right arguments takes precedence on the chosen extrapolation method and will assign the respective left and right values to the given points.

Parameters
  • interpolator (object) – Interpolator object.

  • method (unicode, optional) – {‘Linear’, ‘Constant’}, Extrapolation method.

  • left (numeric, optional) – Value to return for x < xi[0].

  • right (numeric, optional) – Value to return for x > xi[-1].

  • dtype (type) – Data type used for internal conversions.

Methods

Notes

  • The interpolator must define x and y attributes.

References

[sastanin], [WRC12d]

Examples

Extrapolating a single numeric variable:

>>> from colour.algebra import LinearInterpolator
>>> x = np.array([3, 4, 5])
>>> y = np.array([1, 2, 3])
>>> interpolator = LinearInterpolator(x, y)
>>> extrapolator = Extrapolator(interpolator)
>>> extrapolator(1)
-1.0

Extrapolating an array_like variable:

>>> extrapolator(np.array([6, 7 , 8]))
array([ 4.,  5.,  6.])

Using the Constant extrapolation method:

>>> x = np.array([3, 4, 5])
>>> y = np.array([1, 2, 3])
>>> interpolator = LinearInterpolator(x, y)
>>> extrapolator = Extrapolator(interpolator, method='Constant')
>>> extrapolator(np.array([0.1, 0.2, 8, 9]))
array([ 1.,  1.,  3.,  3.])

Using defined left boundary and Constant extrapolation method:

>>> x = np.array([3, 4, 5])
>>> y = np.array([1, 2, 3])
>>> interpolator = LinearInterpolator(x, y)
>>> extrapolator = Extrapolator(interpolator, method='Constant', left=0)
>>> extrapolator(np.array([0.1, 0.2, 8, 9]))
array([ 0.,  0.,  3.,  3.])
__init__(interpolator=None, method='Linear', left=None, right=None, dtype=None)[source]
property interpolator

Getter and setter property for the Colour or scipy interpolator class instance.

Parameters

value (callable) – Value to set the Colour or scipy interpolator class instance with.

Returns

Colour or scipy interpolator class instance.

Return type

callable

__weakref__

list of weak references to the object (if defined)

property method

Getter and setter property for the extrapolation method.

Parameters

value (unicode) – Value to set the extrapolation method. with.

Returns

Extrapolation method.

Return type

unicode

property left

Getter and setter property for left value to return for x < xi[0].

Parameters

value (numeric) – Left value to return for x < xi[0].

Returns

Left value to return for x < xi[0].

Return type

numeric

property right

Getter and setter property for right value to return for x > xi[-1].

Parameters

value (numeric) – Right value to return for x > xi[-1].

Returns

Right value to return for x > xi[-1].

Return type

numeric

__call__(x)[source]

Evaluates the Extrapolator at given point(s).

Parameters

x (numeric or array_like) – Point(s) to evaluate the Extrapolator at.

Returns

Extrapolated points value(s).

Return type

float or ndarray