source: orange/docs/widgets/rst/unsupervized/attributedistance.rst @ 11050:e3c4699ca155

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1.. _Attribute Distance:
2
3Attribute Distance
4==================
5
6.. image:: ../icons/AttributeDistance.png
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8Computes distances between examples in the data set
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10Signals
11-------
12
13Inputs:
14   - Examples
15      A list of examples
16
17
18Outputs:
19   - Distance Matrix
20      A matrix of attribute distances
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22
23Description
24-----------
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26Widget Attribute Distances computes the distances between the attributes in the data sets. Don't confuse it with a similar widget for computing the distances between examples.
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28.. image:: images/AttributeDistance.png
29   :alt: Association Rules Widget
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31Since the widget cannot compute distances between discrete and continuous attributes, all attributes are first either discretized, by splitting the attribute into four quartiles, or "continuized" by treating any discrete attributes as ordinal with values equivalent to 0, 1, 2, 3... For other, possibly better methods of discretization/continuization, see widgets `Discretize <../Data/Discretize.htm>`_ and `Continuize <../Data/Continuize.htm>`_.
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33The two kinds of attributes then have different measures of distance.
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35For discrete attributes, the distance can be computed as :obj:`Pearson's chi-square`, where the more the two attributes are dependent, the closer they are. The measure actually returns the p-value of the common chi-square test of independence. The other two measures are as defined by Aleks Jakulin in his work on `attribute interactions <http://stat.columbia.edu/~jakulin/Int/>`_: :obj:`2-way interaction` is defined as I(A;B)/H(A,B) and :obj:`3-way interaction` is I(A;B;C), respectively.
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38Examples
39--------
40
41This widget is an intermediate widget: it shows no user readable results and its output needs to be fed to a widget that can do something useful with the computed distances, for instance the `Distance Map <DistanceMap.htm>`_, `Hierarchical Clustering <HierarchicalClustering.htm>`_ to cluster the attributes, or `MDS <MDS.htm>`_ to visualize the distances between them.
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43.. image:: images/AttributeDistance-Schema.png
44   :alt: Association Rules
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