96 lines
5.4 KiB
Plaintext
96 lines
5.4 KiB
Plaintext
---
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title: PCAExtrapolator (v0.26)
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description: API reference for qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator in qiskit v0.26
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator
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---
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<span id="qiskit-chemistry-algorithms-pes-samplers-pcaextrapolator" />
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# qiskit.chemistry.algorithms.pes\_samplers.PCAExtrapolator
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<Class id="qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-aqua/tree/stable/0.9/qiskit/chemistry/algorithms/pes_samplers/extrapolator.py" signature="PCAExtrapolator(extrapolator=None, kernel=None, window=2)" modifiers="class">
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A wrapper extrapolator which reduces the points’ dimensionality with PCA, performs extrapolation in the transformed pca space, and inverse transforms the results before returning. A user specifies the kernel within how the PCA transformation should be done.
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Constructor.
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**Parameters**
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* **extrapolator** (`Union`\[`PolynomialExtrapolator`, `DifferentialExtrapolator`, `None`]) – ‘internal’ extrapolator that performs extrapolation on variational parameters based on data window.
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* **kernel** (`Optional`\[`str`]) – Kernel (from sklearn) that specifies how dimensionality reduction should be done for PCA. Default value is None, and switches the extrapolation to standard PCA.
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* **window** (`int`) – Number of previous points to use for extrapolation.
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**Raises**
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[**AquaError**](qiskit.aqua.AquaError "qiskit.aqua.AquaError") – if kernel is not defined in sklearn module.
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### \_\_init\_\_
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<Function id="qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.__init__" signature="__init__(extrapolator=None, kernel=None, window=2)">
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Constructor.
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**Parameters**
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* **extrapolator** (`Union`\[`PolynomialExtrapolator`, `DifferentialExtrapolator`, `None`]) – ‘internal’ extrapolator that performs extrapolation on variational parameters based on data window.
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* **kernel** (`Optional`\[`str`]) – Kernel (from sklearn) that specifies how dimensionality reduction should be done for PCA. Default value is None, and switches the extrapolation to standard PCA.
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* **window** (`int`) – Number of previous points to use for extrapolation.
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**Raises**
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[**AquaError**](qiskit.aqua.AquaError "qiskit.aqua.AquaError") – if kernel is not defined in sklearn module.
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</Function>
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## Methods
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| | |
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| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- |
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| [`__init__`](#qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.__init__ "qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.__init__")(\[extrapolator, kernel, window]) | Constructor. |
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| [`extrapolate`](#qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.extrapolate "qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.extrapolate")(points, param\_dict) | Extrapolate at specified point of interest given a set of variational parameters. |
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| [`factory`](#qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.factory "qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.factory")(mode, \*\*kwargs) | Factory method for constructing extrapolators. |
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### extrapolate
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<Function id="qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.extrapolate" signature="extrapolate(points, param_dict)">
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Extrapolate at specified point of interest given a set of variational parameters. This method transforms the parameters in PCA space before performing the internal extrapolation. The parameters are transformed back to regular space after extrapolation.
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**Parameters**
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* **points** (`List`\[`float`]) – List of point(s) to be used for extrapolation. Can represent some degree of freedom, ex, interatomic distance.
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* **param\_dict** (`Optional`\[`Dict`\[`float`, `List`\[`float`]]]) – Dictionary of variational parameters. Each key is the point
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* **the value is a list of the variational parameters.** (*and*) –
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**Return type**
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`Dict`\[`float`, `List`\[`float`]]
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**Returns**
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Dictionary of variational parameters for extrapolated point(s).
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</Function>
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### factory
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<Function id="qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator.factory" signature="factory(mode, **kwargs)" modifiers="static">
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Factory method for constructing extrapolators.
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**Parameters**
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* **mode** (`str`) – Extrapolator to instantiate. Can be one of: - ‘window’ - ‘poly’ - ‘diff\_model’ - ‘pca’ - ‘l1’
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* **kwargs** – arguments to be passed to the constructor of an extrapolator
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**Return type**
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`Extrapolator`
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**Returns**
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A newly created extrapolator instance.
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**Raises**
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[**AquaError**](qiskit.aqua.AquaError "qiskit.aqua.AquaError") – if specified mode is unknown.
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</Function>
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</Class>
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