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java.lang.Objectde.fu_berlin.ties.classify.feature.FeatureTransformer
de.fu_berlin.ties.classify.feature.SBPHTransformer
public class SBPHTransformer
Transforms a feature vector using a simple implementation of the sparse binary polynomial hashing (SBPH) technique introduced by CRM114. This transformer discard all comment-only features (indeed all comments). It slides of window of length N over the remaining original features. For each window position, it counts in binary from 1 to 2N. For each odd number, a joint feature is generated where original features at "1" positions are visible and original features at "0" positions are hidden. Separators prior to the first feature are discarded, but all inner separators are kept. E.g. if N=3 and a pipe character "|" is used as separator, from the original features "a", "b", "c", four joint features will be generated at the last position: "c" (binary 1=001), "b|c" (binary 3=011), "a||c" (binary 5=101), "a|b|c" (binary 7=111). Thus 2N-1 joint features are generated for each original (non-comment) feature (except for the very first features).
Instances of this class are thread-safe.
Field Summary | |
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static String |
DEFAULT_SEPARATOR
The separator used by default (a space character). |
Fields inherited from class de.fu_berlin.ties.classify.feature.FeatureTransformer |
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CONFIG_TRANSFORMERS, ELEMENT_MAIN |
Constructor Summary | |
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SBPHTransformer(Element element)
Creates a new instance from an XML element, fulfilling the recommandation of the XMLStorable interface. |
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SBPHTransformer(FeatureTransformer precTrans,
int len,
String sep)
Creates a new instance. |
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SBPHTransformer(FeatureTransformer precTrans,
TiesConfiguration config)
Creates a new instance. |
Method Summary | |
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protected FeatureVector |
doTransform(FeatureVector orgFeatures)
Transforms a feature vector. |
int |
getLength()
Returns the maximum number of original features joined. |
String |
getSeparator()
Returns the string used to separate original features (by default a space character). |
ObjectElement |
toElement()
Stores all relevant fields of this object in an XML element for serialization. An equivalent object can be created by calling ObjectElement.createObject(org.dom4j.Element,
Class) on the created element. |
String |
toString()
Returns a string representation of this object. |
Methods inherited from class de.fu_berlin.ties.classify.feature.FeatureTransformer |
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createTransformer, createTransformer, getPrecedingTransformer, transform |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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public static final String DEFAULT_SEPARATOR
Constructor Detail |
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public SBPHTransformer(Element element) throws InstantiationException
XMLStorable
interface.
element
- the XML element containing the serialized representation
InstantiationException
- if the given element does not contain
a valid transformer descriptionpublic SBPHTransformer(FeatureTransformer precTrans, int len, String sep)
precTrans
- the preceding transformer to use if this transformer
is part of a chain; null
otherwiselen
- the maximum number of original features joinedsep
- the string used to separate original features -- this string
should never occur within original featurespublic SBPHTransformer(FeatureTransformer precTrans, TiesConfiguration config)
precTrans
- the preceding transformer to use if this transformer
is part of a chain; null
otherwiseconfig
- used to configure this instanceMethod Detail |
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protected FeatureVector doTransform(FeatureVector orgFeatures)
doTransform
in class FeatureTransformer
orgFeatures
- the original feature vector to transform
public int getLength()
public String getSeparator()
public ObjectElement toElement()
ObjectElement.createObject(org.dom4j.Element,
Class)
on the created element.
toElement
in interface XMLStorable
toElement
in class FeatureTransformer
public String toString()
toString
in class FeatureTransformer
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