Orange.classification.constant.rst

.. py:currentmodule:: Orange.classification

Constant Classifier

Constant classifier always predicts the same value. It is constructed by various learners such as :obj:`~Orange.classification.majority.MajorityLearner`, and also used in other places.

Always predict the specified default_val or default_distribution, disregarding the instance.

.. attribute:: class_var

    Class variable that the classifier predicts.

.. attribute:: default_val

    The value returned by the classifier.

.. attribute:: default_distribution

    Class probabilities returned by the classifier.

.. method:: __init__(variable, value, distribution)

    Constructor can be called without arguments, with a
    variable, value or both. If the value is given and is of type
    :obj:`Orange.data.Value`, its attribute
    :obj:`Orange.data.Value.variable` will either be used for
    initializing
    :obj:`~Orange.classification.ConstantClassifier.variable` or
    checked against it, if :obj:`variable` is given as an
    argument.

    :param variable: Class variable that the classifier predicts.
    :type variable: :obj:`Orange.feature.Descriptor`
    :param value: Value returned by the classifier.
    :type value: :obj:`Orange.data.Value` or int (index) or float
    :param distribution: Class probabilities returned by the classifier.
    :type dstribution: :obj:`Orange.statistics.distribution.Distribution`

.. method:: __call__(instance, return_type)

    Return :obj:`default_val` and/or :obj:`default_distribution`
    (depending upon :obj:`return_type`) disregarding the
    :obj:`instance`.