source: orange/docs/widgets/rst/data/selectdata.rst @ 11778:ecd4beec2099

Revision 11778:ecd4beec2099, 2.5 KB checked in by Ales Erjavec <ales.erjavec@…>, 5 months ago (diff)

Use new SVG icons in the widget documentation.

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1.. _Select Data:
2
3Select Data
4===========
5
6.. image:: ../../../../Orange/OrangeWidgets/Data/icons/SelectData.svg
7
8Selects instances from input data sets based on conditions on attributes.
9
10Signals
11-------
12
13Inputs:
14   - Examples (ExampleTable)
15      Attribute-valued data set.
16
17
18Outputs:
19   - Matching Examples (ExampleTable)
20      Attribute-valued data set composed from instances from input data set
21      that match user-defined condition.
22   - Non-Matching Examples (ExampleTable)
23      Data instances from input data set that do not match the user-defined
24      condition.
25
26
27Description
28-----------
29
30This widget allows the user to select a subset of the data from the
31input data set based on the condition defined over a set of data's
32attributes. Data instances that match the selection rule are placed on
33the output channel.
34
35.. image:: images/SelectData.png
36   :alt: Select Data
37
38Condition is presented in disjunctive normal form, that is, as
39collection of conjuncted terms (AND operator) with optional disjunction
40(OR operator). In other words, if condition does not include a
41disjunction (OR line in the condition) than selected items are those
42matching all terms in the condition.
43
44Condition terms are defined through selecting of an attribute,
45selecting an operator from the list of operators that apply to
46attribute's type, and, if needed, defining the value to be used in
47condition term. Operators are different for discrete, continuous and
48string attributes.
49
50After the terms is defined, it is included in the condition by
51pressing :obj:`Add button`.
52
53To update or change the condition term, select the corresponding
54line in the :obj:`Data Selection Criteria`, change the term's definition
55(:obj:`Attribute`/:obj:`Operator`/:obj:`Values`) and press :obj:`Update`.
56
57Notice that any change in composition of the condition will trigger
58updates in information pane that displays the number of data instances
59being selected (:obj:`Data Out`). Number of instances that match specific
60condition terms are also displayed at the start of the condition term
61line.
62
63Data set composed of instances that match the defined condition is
64placed on the output channel. If :obj:`Update on any change` is selected,
65than the output is updated on any change in the composition of the
66condition or any of its terms.
67
68Examples
69--------
70
71Below is a simple example that loads the imports-85 data set and
72compares the lengths of the car in a complete data set and data set
73where some more expensive brands are selected.
74
75.. image:: images/SelectData-Example-S.gif
76   :alt: Schema with Data Sampler
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