.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_examples/swissmetro/plot_b28_parameter_overrides.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_auto_examples_swissmetro_plot_b28_parameter_overrides.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_examples_swissmetro_plot_b28_parameter_overrides.py:

.. _plot_b28_parameter_overrides:

28. Explicit parameter overrides in a simple model
===================================================

This example illustrates the preprocessing API used to control parameters in
an expression.  The override is applied before the expression is passed to
``BIOGEME``; estimation itself is unchanged.

Two types of control are shown:

* ``b_cost`` is replaced by a fixed ``Beta`` with a user-supplied initial
  value and bounds;
* ``asc_train`` is replaced by ``Numeric(0)``, so it is no longer an estimated
  parameter.

The same mechanism can later be used with parameters generated by catalogs,
assisted specification, or latent-variable builders.

Michel Bierlaire, EPFL

.. GENERATED FROM PYTHON SOURCE LINES 22-50

.. code-block:: Python


    from swissmetro_data import (
        CAR_AV_SP,
        CAR_CO_SCALED,
        CAR_TT_SCALED,
        CHOICE,
        SM_AV,
        SM_COST_SCALED,
        SM_TT_SCALED,
        TRAIN_AV_SP,
        TRAIN_COST_SCALED,
        TRAIN_TT_SCALED,
        database,
    )

    import biogeme.biogeme_logging as blog
    from biogeme.biogeme import BIOGEME
    from biogeme.expressions import (
        Beta,
        Numeric,
        ParameterOverrides,
        apply_parameter_overrides,
    )
    from biogeme.models import loglogit

    logger = blog.get_screen_logger(level=blog.INFO)
    logger.info('Example plot_b28_parameter_overrides.py')


.. GENERATED FROM PYTHON SOURCE LINES 51-52

Define the ordinary multinomial-logit specification.

.. GENERATED FROM PYTHON SOURCE LINES 52-65

.. code-block:: Python

    asc_car = Beta('asc_car', 0, None, None, 0)
    asc_train = Beta('asc_train', 0, None, None, 0)
    b_time = Beta('b_time', 0, None, None, 0)
    b_cost = Beta('b_cost', 0, None, None, 0)

    v_train = asc_train + b_time * TRAIN_TT_SCALED + b_cost * TRAIN_COST_SCALED
    v_swissmetro = b_time * SM_TT_SCALED + b_cost * SM_COST_SCALED
    v_car = asc_car + b_time * CAR_TT_SCALED + b_cost * CAR_CO_SCALED

    utilities = {1: v_train, 2: v_swissmetro, 3: v_car}
    availability = {1: TRAIN_AV_SP, 2: SM_AV, 3: CAR_AV_SP}
    log_probability = loglogit(utilities, availability, CHOICE)


.. GENERATED FROM PYTHON SOURCE LINES 66-69

Explicitly control parameters before creating the BIOGEME object.  The key
is the original Beta name.  A replacement can be a full Beta definition or
any other valid Biogeme expression.

.. GENERATED FROM PYTHON SOURCE LINES 69-75

.. code-block:: Python

    overrides = ParameterOverrides()
    overrides.set('b_cost', Beta('b_cost', -1.0, -10.0, 0.0, 1))
    overrides.set('asc_train', Numeric(0))

    log_probability = apply_parameter_overrides(log_probability, overrides)


.. GENERATED FROM PYTHON SOURCE LINES 76-77

Estimate the resulting model.

.. GENERATED FROM PYTHON SOURCE LINES 77-83

.. code-block:: Python

    biogeme = BIOGEME(database, log_probability)
    biogeme.model_name = 'b28_parameter_overrides'
    results = biogeme.estimate()

    print(results.short_summary())
    print(results.get_beta_values())


.. _sphx_glr_download_auto_examples_swissmetro_plot_b28_parameter_overrides.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_b28_parameter_overrides.ipynb <plot_b28_parameter_overrides.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_b28_parameter_overrides.py <plot_b28_parameter_overrides.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_b28_parameter_overrides.zip <plot_b28_parameter_overrides.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_