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## weka.classifiers.rules
Class RuleStats

    java.lang.Object
      weka.classifiers.rules.RuleStats

All Implemented Interfaces:
  java.io.Serializable, RevisionHandler

    public class RuleStats

extends java.lang.Object
implements java.io.Serializable, RevisionHandler

This class implements the statistics functions used in the propositional rule learner, from the simpler ones like count of true/false positive/negatives, filter data based on the ruleset, etc. to the more sophisticated ones such as MDL calculation and rule variants generation for each rule in the ruleset.

Obviously the statistics functions listed above need the specific data and the specific ruleset, which are given in order to instantiate an object of this class.

Version:
  $Revision: 4608 $
Author:
  Xin Xu (xx5@cs.waikato.ac.nz)
See Also:
  Serialized Form

Constructor Summary
`RuleStats()` Default constructor
`RuleStats(Instances data, FastVector rules)` Constructor that provides ruleset and data

Method Summary
`void` | `addAndUpdate(Rule lastRule)` Add a rule to the ruleset and update the stats
`void` | `cleanUp()` Frees up memory after classifier has been built.
`double` | `combinedDL(double expFPRate, double predicted)` Compute the combined DL of the ruleset in this class, i.e.
`void` | `countData()` Filter the data according to the ruleset and compute the basic stats: coverage/uncoverage, true/false positive/negatives of each rule
`void` | `countData(int index, Instances uncovered, double[][] prevRuleStats)` Count data from the position index in the ruleset assuming that given data are not covered by the rules in position 0...(index-1), and the statistics of these rules are provided.
This procedure is typically useful when a temporary object of RuleStats is constructed in order to efficiently calculate the relative DL of rule in position index, thus all other stuff is not needed.
`static double` | `dataDL(double expFPOverErr, double cover, double uncover, double fp, double fn)` The description length of data given the parameters of the data based on the ruleset.
`Instances` | `getData()` Get the data of the stats
`double[]` | `getDistributions(int index)` Get the class distribution predicted by the rule in given position
`Instances[]` | `getFiltered(int index)` Get the data after filtering the given rule
`java.lang.String` | `getRevision()` Returns the revision string.
`FastVector` | `getRuleset()` Get the ruleset of the stats
`int` | `getRulesetSize()` Get the size of the ruleset in the stats
`double[]` | `getSimpleStats(int index)` Get the simple stats of one rule, including 6 parameters: 0: coverage; 1:uncoverage; 2: true positive; 3: true negatives; 4: false positives; 5: false negatives
`double` | `minDataDLIfDeleted(int index, double expFPRate, boolean checkErr)` Compute the minimal data description length of the ruleset if the rule in the given position is deleted. The min_data_DL_if_deleted = data_DL_if_deleted - potential
`double` | `minDataDLIfExists(int index, double expFPRate, boolean checkErr)` Compute the minimal data description length of the ruleset if the rule in the given position is NOT deleted. The min_data_DL_if_n_deleted = data_DL_if_n_deleted - potential
`static double` | `numAllConditions(Instances data)` Compute the number of all possible conditions that could appear in a rule of a given data.
`static Instances[]` | `partition(Instances data, int numFolds)` Patition the data into 2, first of which has (numFolds-1)/numFolds of the data and the second has 1/numFolds of the data
`double` | `potential(int index, double expFPOverErr, double[] rulesetStat, double[] ruleStat, boolean checkErr)` Calculate the potential to decrease DL of the ruleset, i.e.
`void` | `reduceDL(double expFPRate, boolean checkErr)` Try to reduce the DL of the ruleset by testing removing the rules one by one in reverse order and update all the stats
`double` | `relativeDL(int index, double expFPRate, boolean checkErr)` The description length (DL) of the ruleset relative to if the rule in the given position is deleted, which is obtained by: MDL if the rule exists - MDL if the rule does not exist Note the minimal possible DL of the ruleset is calculated(i.e.
`void` | `removeLast()` Remove the last rule in the ruleset as well as it's stats.
`static Instances` | `rmCoveredBySuccessives(Instances data, FastVector rules, int index)` Static utility function to count the data covered by the rules after the given index in the given rules, and then remove them.
`void` | `setData(Instances data)` Set the data of the stats, overwriting the old one if any
`void` | `setMDLTheoryWeight(double weight)` Set the weight of theory in MDL calcualtion
`void` | `setNumAllConds(double total)` Set the number of all conditions that could appear in a rule in this RuleStats object, if the number set is smaller than 0 (typically -1), then it calcualtes based on the data store
`void` | `setRuleset(FastVector rules)` Set the ruleset of the stats, overwriting the old one if any
`static Instances` | `stratify(Instances data, int folds, java.util.Random rand)` Stratify the given data into the given number of bags based on the class values.
`static double` | `subsetDL(double t, double k, double p)` Subset description length: S(t,k,p) = -k*log2(p)-(n-k)log2(1-p) Details see Quilan: "MDL and categorical theories (Continued)",ML95
`double` | `theoryDL(int index)` The description length of the theory for a given rule.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### RuleStats

    public RuleStats()

  Default constructor

### RuleStats

    public RuleStats(Instances data,
                     FastVector rules)

  Constructor that provides ruleset and data

  Parameters:
    `data` - the data
    `rules` - the ruleset

Method Detail

### cleanUp

    public void cleanUp()

  Frees up memory after classifier has been built.

### setNumAllConds

    public void setNumAllConds(double total)

  Set the number of all conditions that could appear in a rule in this RuleStats object, if the number set is smaller than 0 (typically -1), then it calcualtes based on the data store

  Parameters:
    `total` - the set number

### setData

    public void setData(Instances data)

  Set the data of the stats, overwriting the old one if any

  Parameters:
    `data` - the data to be set

### getData

    public Instances getData()

  Get the data of the stats

  Returns:
    the data

### setRuleset

    public void setRuleset(FastVector rules)

  Set the ruleset of the stats, overwriting the old one if any

  Parameters:
    `rules` - the set of rules to be set

### getRuleset

    public FastVector getRuleset()

  Get the ruleset of the stats

  Returns:
    the set of rules

### getRulesetSize

    public int getRulesetSize()

  Get the size of the ruleset in the stats

  Returns:
    the size of ruleset

### getSimpleStats

    public double[] getSimpleStats(int index)

  Get the simple stats of one rule, including 6 parameters: 0: coverage; 1:uncoverage; 2: true positive; 3: true negatives; 4: false positives; 5: false negatives

  Parameters:
    `index` - the index of the rule
  Returns:
    the stats

### getFiltered

    public Instances[] getFiltered(int index)

  Get the data after filtering the given rule

  Parameters:
    `index` - the index of the rule
  Returns:
    the data covered and uncovered by the rule

### getDistributions

    public double[] getDistributions(int index)

  Get the class distribution predicted by the rule in given position

  Parameters:
    `index` - the position index of the rule
  Returns:
    the class distributions

### setMDLTheoryWeight

    public void setMDLTheoryWeight(double weight)

  Set the weight of theory in MDL calcualtion

  Parameters:
    `weight` - the weight to be set

### numAllConditions

    public static double numAllConditions(Instances data)

  Compute the number of all possible conditions that could appear in a rule of a given data. For nominal attributes, it's the number of values that could appear; for numeric attributes, it's the number of values * 2, i.e. <= and >= are counted as different possible conditions.

  Parameters:
    `data` - the given data
  Returns:
    number of all conditions of the data

### countData

    public void countData()

  Filter the data according to the ruleset and compute the basic stats: coverage/uncoverage, true/false positive/negatives of each rule

### countData

    public void countData(int index,
                          Instances uncovered,
                          double[][] prevRuleStats)

  Count data from the position index in the ruleset assuming that given data are not covered by the rules in position 0...(index-1), and the statistics of these rules are provided.
  This procedure is typically useful when a temporary object of RuleStats is constructed in order to efficiently calculate the relative DL of rule in position index, thus all other stuff is not needed.

  Parameters:
    `index` - the given position
    `uncovered` - the data not covered by rules before index
    `prevRuleStats` - the provided stats of previous rules

### addAndUpdate

    public void addAndUpdate(Rule lastRule)

  Add a rule to the ruleset and update the stats

  Parameters:
    `lastRule` - the rule to be added

### subsetDL

    public static double subsetDL(double t,
                                  double k,
                                  double p)

  Subset description length:
  S(t,k,p) = -k*log2(p)-(n-k)log2(1-p) Details see Quilan: "MDL and categorical theories (Continued)",ML95

  Parameters:
    `t` - the number of elements in a known set
    `k` - the number of elements in a subset
    `p` - the expected proportion of subset known by recipient
  Returns:
    the subset description length

### theoryDL

    public double theoryDL(int index)

  The description length of the theory for a given rule. Computed as:
  0.5* [||k||+ S(t, k, k/t)]
  where k is the number of antecedents of the rule; t is the total possible antecedents that could appear in a rule; ||K|| is the universal prior for k , log2*(k) and S(t,k,p) = -k*log2(p)-(n-k)log2(1-p) is the subset encoding length.

  Details see Quilan: "MDL and categorical theories (Continued)",ML95

  Parameters:
    `index` - the index of the given rule (assuming correct)
  Returns:
    the theory DL, weighted if weight != 1.0

### dataDL

    public static double dataDL(double expFPOverErr,
                                double cover,
                                double uncover,
                                double fp,
                                double fn)

  The description length of data given the parameters of the data based on the ruleset.

  Details see Quinlan: "MDL and categorical theories (Continued)",ML95

  Parameters:
    `expFPOverErr` - expected FP/(FP+FN)
    `cover` - coverage
    `uncover` - uncoverage
    `fp` - False Positive
    `fn` - False Negative
  Returns:
    the description length

### potential

    public double potential(int index,
                            double expFPOverErr,
                            double[] rulesetStat,
                            double[] ruleStat,
                            boolean checkErr)

  Calculate the potential to decrease DL of the ruleset, i.e. the possible DL that could be decreased by deleting the rule whose index and simple statstics are given. If there's no potentials (i.e. smOrEq 0 && error rate < 0.5), it returns NaN.

  The way this procedure does is copied from original RIPPER implementation and is quite bizzare because it does not update the following rules' stats recursively any more when testing each rule, which means it assumes after deletion no data covered by the following rules (or regards the deleted rule as the last rule). Reasonable assumption?

  Parameters:
    `index` - the index of the rule in m_Ruleset to be deleted
    `expFPOverErr` - expected FP/(FP+FN)
    `rulesetStat` - the simple statistics of the ruleset, updated if the rule should be deleted
    `ruleStat` - the simple statistics of the rule to be deleted
    `checkErr` - whether check if error rate >= 0.5
  Returns:
    the potential DL that could be decreased

### minDataDLIfDeleted

    public double minDataDLIfDeleted(int index,
                                     double expFPRate,
                                     boolean checkErr)

  Compute the minimal data description length of the ruleset if the rule in the given position is deleted.
  The min_data_DL_if_deleted = data_DL_if_deleted - potential

  Parameters:
    `index` - the index of the rule in question
    `expFPRate` - expected FP/(FP+FN), used in dataDL calculation
    `checkErr` - whether check if error rate >= 0.5
  Returns:
    the minDataDL

### minDataDLIfExists

    public double minDataDLIfExists(int index,
                                    double expFPRate,
                                    boolean checkErr)

  Compute the minimal data description length of the ruleset if the rule in the given position is NOT deleted.
  The min_data_DL_if_n_deleted = data_DL_if_n_deleted - potential

  Parameters:
    `index` - the index of the rule in question
    `expFPRate` - expected FP/(FP+FN), used in dataDL calculation
    `checkErr` - whether check if error rate >= 0.5
  Returns:
    the minDataDL

### relativeDL

    public double relativeDL(int index,
                             double expFPRate,
                             boolean checkErr)

  The description length (DL) of the ruleset relative to if the rule in the given position is deleted, which is obtained by:
  MDL if the rule exists - MDL if the rule does not exist
  Note the minimal possible DL of the ruleset is calculated(i.e. some other rules may also be deleted) instead of the DL of the current ruleset.

  Parameters:
    `index` - the given position of the rule in question (assuming correct)
    `expFPRate` - expected FP/(FP+FN), used in dataDL calculation
    `checkErr` - whether check if error rate >= 0.5
  Returns:
    the relative DL

### reduceDL

    public void reduceDL(double expFPRate,
                         boolean checkErr)

  Try to reduce the DL of the ruleset by testing removing the rules one by one in reverse order and update all the stats

  Parameters:
    `expFPRate` - expected FP/(FP+FN), used in dataDL calculation
    `checkErr` - whether check if error rate >= 0.5

### removeLast

    public void removeLast()

  Remove the last rule in the ruleset as well as it's stats. It might be useful when the last rule was added for testing purpose and then the test failed

### rmCoveredBySuccessives

    public static Instances rmCoveredBySuccessives(Instances data,
                                                   FastVector rules,
                                                   int index)

  Static utility function to count the data covered by the rules after the given index in the given rules, and then remove them. It returns the data not covered by the successive rules.

  Parameters:
    `data` - the data to be processed
    `rules` - the ruleset
    `index` - the given index
  Returns:
    the data after processing

### stratify

    public static final Instances stratify(Instances data,
                                           int folds,
                                           java.util.Random rand)

  Stratify the given data into the given number of bags based on the class values. It differs from the `Instances.stratify(int fold)` that before stratification it sorts the instances according to the class order in the header file. It assumes no missing values in the class.

  Parameters:
    `data` - the given data
    `folds` - the given number of folds
    `rand` - the random object used to randomize the instances
  Returns:
    the stratified instances

### combinedDL

    public double combinedDL(double expFPRate,
                             double predicted)

  Compute the combined DL of the ruleset in this class, i.e. theory DL and data DL. Note this procedure computes the combined DL according to the current status of the ruleset in this class

  Parameters:
    `expFPRate` - expected FP/(FP+FN), used in dataDL calculation
    `predicted` - the default classification if ruleset covers null
  Returns:
    the combined class

### partition

    public static final Instances[] partition(Instances data,
                                              int numFolds)

  Patition the data into 2, first of which has (numFolds-1)/numFolds of the data and the second has 1/numFolds of the data

  Parameters:
    `data` - the given data
    `numFolds` - the given number of folds
  Returns:
    the patitioned instances

### getRevision

    public java.lang.String getRevision()

  Returns the revision string.

  Specified by:
    `getRevision` in interface `RevisionHandler`
  Returns:
    the revision

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