source: orange/docs/widgets/rst/data/selectdata.rst @ 11050:e3c4699ca155

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