Changeset 3581:43b7e67f3099 in orange


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Timestamp:
04/24/07 23:17:45 (7 years ago)
Author:
janezd <janez.demsar@…>
Branch:
default
Convert:
1d714383a26796481ef9cd6ae5bb2e26773ff771
Message:
  • described Preprocessor_shuffle
File:
1 edited

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  • orange/doc/reference/preprocessing.htm

    r3083 r3581  
    169169<P>There are four preprocessors that select or remove examples with missing values. <CODE><INDEX name="classes/Preprocessor_dropMissing">Preprocessor_dropMissing</CODE> removes examples with any missing values and <CODE><INDEX name="classes/Preprocessor_dropMissingClasses">Preprocessor_dropMissingClasses</CODE> removes examples with missing the class value. The other pair is <CODE><INDEX name="classes/Preprocessor_takeMissing">Preprocessor_takeMissing</CODE> and <CODE><INDEX name="classes/Preprocessor_takeMissingClasses">Preprocessor_takeMissingClasses</CODE> that select only examples with at least one missing value or without class value, respectively. See examples in the section about <a href="#adding_missing_values">adding missing values</A>.</P> 
    170170 
     171 
     172<H2>Shuffling</H2> 
     173<index name="preprocessing/shuffling attribute values"> 
     174<index name="shuffle" 
     175 
     176<P>Some statistical tests require making a certain attribute useless by permuting its values across examples. There is a preprocessor to do this, called <code>Preprocessor_shuffle</code>.</P> 
     177 
     178<P class=section>Attributes</P> 
     179<DL class=attributes> 
     180<DT>attributes</DT> 
     181<DD>A list of attributes (usually a single attribute) whose values need to be shuffled.</DD> 
     182</DL> 
     183 
     184<P>Here's how to use it:</P> 
     185<xmp class="code">d2 = orange.Preprocessor_shuffle(d, attributes=[d.domain[0]])</xmp> 
     186 
     187<P>Executing this will create a new table <code>d2</code>, which will contain all examples from <code>d</code> but with the values of the first attribute permuted.</P> 
    171188 
    172189<H2>Adding noise</H2> 
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