source: orange/Orange/doc/widgets/Data/SelectData.htm @ 9671:a7b056375472

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1<html>
2<head>
3<title>Select Data</title>
4<link rel=stylesheet href="../../../style.css" type="text/css" media=screen>
5<link rel=stylesheet href="style-print.css" type="text/css" media=print></link>
6</head>
7
8<body>
9
10<h1>Select Data</h1>
11
12<img class="screenshot" src="../icons/SelectData.png">
13<p>Selects instances from input data sets based on conditions on attributes.</p>
14
15<h2>Channels</h2>
16
17<h3>Inputs</h3>
18
19<DL class=attributes>
20<DT>Examples (ExampleTable)</DT>
21<DD>Attribute-valued data set.</DD>
22</dl>
23
24<h3>Outputs</h3>
25
26<DL class=attributes>
27<DT>Matching Examples (ExampleTable)</DT>
28<DD>Attribute-valued data set composed from instances from input data set that match user-defined condition.</DD>
29<DT>Non-Matching Examples (ExampleTable)</DT>
30<DD>Data instances from input data set that do not match the user-defined condition.</DD>
31</dl>
32
33<h2>Description</h2>
34
35<p>This widget allows the user to select a subset of the data from the
36input data set based on the condition defined over a set of data's
37attributes. Data instances that match the selection rule are placed on
38the output channel.</p>
39
40<img class="screenshot"
41src="SelectData.png" alt="Select Data" border=0>
42
43<p>Condition is presented in disjunctive normal form, that is, as
44collection of conjuncted terms (AND operator) with optional disjunction
45(OR operator). In other words, if condition does not include a
46disjunction (OR line in the condition) than selected items are those
47matching all terms in the condition.</p>
48
49<p>Condition terms are defined through selecting of an attribute,
50selecting an operator from the list of operators that apply to
51attribute's type, and, if needed, defining the value to be used in
52condition term. Operators are different for discrete, continuous and
53string attributes.</p>
54
55<p>After the terms is defined, it is included in the condition by
56pressing <span class="option">Add button</span>.</p>
57
58<p>To update or change the condition term, select the corresponding
59line in the <span class="option">Data Selection Criteria</span>, change the term's definition
60(<span class="option">Attribute</span>/<span class="option">Operator</span>/<span class="option">Values</span>) and press <span class="option">Update</span>.</p>
61
62<p>Notice that any change in composition of the condition will trigger
63updates in information pane that displays the number of data instances
64being selected (<span class="option">Data Out</span>). Number of instances that match specific
65condition terms are also displayed at the start of the condition term
66line.</p>
67
68<p>Data set composed of instances that match the defined condition is
69placed on the output channel. If <span class="option">Update on any change</span> is selected,
70than the output is updated on any change in the composition of the
71condition or any of its terms.</p>
72
73<h2>Examples</h2>
74
75<p>Below is a simple example that loads the imports-85 data set and
76compares the lengths of the car in a complete data set and data set
77where some more expensive brands are selected.</p>
78
79<a href="SelectData-Example.gif"><img src="SelectData-Example-S.gif"
80alt="Schema with Data Sampler" class="screenshot" border=0></a>
81
82</body>
83</html>
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