Postprocessing
**************
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      Postprocessing refers to evaluations and checks performed on a model to get an understanding of its properties and estimate its quality.
      The BayesValidRox class :any:`bayesvalidrox.post_processing.post_processing.PostProcessing` includes functions that are applicable to all types of surrogate model.
		 
      * ``valid_metamodel``: visualizing some metamodel runs against the corresponding model runs
      * ``check_accuracy``: computing the RMSE error of the surrogate model
		 
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      .. image:: ./diagrams/postprocessing.png
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         :alt: UML diagram for the classes and functions used in active learning in BayesValidRox.
		
Postprocessing methods that are specific to a type of surrogate or training include

* ``plot_moments``: visualizing the moments of a polynomial chaos expansion (PCE, aPCE)
* ``sobol_indices``: calculating the Sobol' and Total Sobol' indices (PCE, aPCE)
* ``plot_seq_design_diagnostics``: visualizing diagnostics that were evaluated during sequential training (surrogate trained with ``train_sequential``)

		 
Example
=======
We want to compare out trained surrogate from :any:`al_description` against its original model.

>>> from bayesvalidrox import PostProcessing

The postprocessing object expects the full engine. This allows it to perform both sampling, running the model and running the surrogate model.

>>> PostProc = PostProcessing(Engine_)

To gain an understanding of the approximation quality we use both ``valid_metamodel`` and ``check_accuracy``.

>>> PostProc.valid_metamodel(n_samples=1)
>>> PostProc.check_accuracy(n_samples=10)

The visual comparison of model and metamodel results is saved in the folder ``Outputs_PostProcessing_calib``, while the accuracy check is given as console output.

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         >>>>> Errors of A <<<<<

         Index  |  RMSE   |  Validation Error
         -----------------------------------
         1  |  1.513e-07  |  2.224e-15

         >>>>> Errors of B <<<<<

         Index  |  RMSE   |  Validation Error
         -----------------------------------
         1  |  5.045e-05  |  2.406e-11
		 
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      .. image:: ../examples/user_guide/Outputs_PostProcessing_calib/Model_vs_PCEModel_y_1.pdf
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         :alt: Visual comparison of model and metamodel outputs