# colour.Extrapolator¶

class colour.Extrapolator(interpolator=None, method='Linear', left=None, right=None, dtype=<class 'numpy.float64'>)[source]

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.

__class__()

Notes

• The interpolator must define x and y attributes.

References

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=<class 'numpy.float64'>)[source]

Initialize self. See help(type(self)) for accurate signature.

Methods

 __init__([interpolator, method, left, …]) Initialize self.

Attributes

 interpolator Getter and setter property for the Colour or scipy interpolator class instance. left Getter and setter property for left value to return for x < xi[0]. method Getter and setter property for the extrapolation method. right Getter and setter property for right value to return for x > xi[-1].