weka.classifiers.evaluation

## Class ThresholdCurve

- java.lang.Object
- - weka.classifiers.evaluation.ThresholdCurve

- All Implemented Interfaces:
    RevisionHandler

      public class ThresholdCurve
      extends java.lang.Object
      implements RevisionHandler

  Generates points illustrating prediction tradeoffs that can be obtained by varying the threshold value between classes. For example, the typical threshold value of 0.5 means the predicted probability of "positive" must be higher than 0.5 for the instance to be predicted as "positive". The resulting dataset can be used to visualize precision/recall tradeoff, or for ROC curve analysis (true positive rate vs false positive rate). Weka just varies the threshold on the class probability estimates in each case. The Mann Whitney statistic is used to calculate the AUC.
  Version:
    $Revision: 10153 $
  Author:
    Len Trigg (len@reeltwo.com)

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static java.lang.String` | `FALLOUT_NAME` attribute name: Fallout
    `static java.lang.String` | `FALSE_NEG_NAME` attribute name: False Negatives
    `static java.lang.String` | `FALSE_POS_NAME` attribute name: False Positives
    `static java.lang.String` | `FMEASURE_NAME` attribute name: FMeasure
    `static java.lang.String` | `FP_RATE_NAME` attribute name: False Positive Rate"
    `static java.lang.String` | `LIFT_NAME` attribute name: Lift
    `static java.lang.String` | `PRECISION_NAME` attribute name: Precision
    `static java.lang.String` | `RECALL_NAME` attribute name: Recall
    `static java.lang.String` | `RELATION_NAME` The name of the relation used in threshold curve datasets
    `static java.lang.String` | `SAMPLE_SIZE_NAME` attribute name: Sample Size
    `static java.lang.String` | `THRESHOLD_NAME` attribute name: Threshold
    `static java.lang.String` | `TP_RATE_NAME` attribute name: True Positive Rate
    `static java.lang.String` | `TRUE_NEG_NAME` attribute name: True Negatives
    `static java.lang.String` | `TRUE_POS_NAME` attribute name: True Positives

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ThresholdCurve()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Instances` | `getCurve(java.util.ArrayList<Prediction> predictions)` Calculates the performance stats for the default class and return results as a set of Instances.
    `Instances` | `getCurve(java.util.ArrayList<Prediction> predictions, int classIndex)` Calculates the performance stats for the desired class and return results as a set of Instances.
    `static double` | `getNPointPrecision(Instances tcurve, int n)` Calculates the n point precision result, which is the precision averaged over n evenly spaced (w.r.t recall) samples of the curve.
    `static double` | `getPRCArea(Instances tcurve)` Calculates the area under the precision-recall curve (AUPRC).
    `java.lang.String` | `getRevision()` Returns the revision string.
    `static double` | `getROCArea(Instances tcurve)` Calculates the area under the ROC curve as the Wilcoxon-Mann-Whitney statistic.
    `static int` | `getThresholdInstance(Instances tcurve, double threshold)` Gets the index of the instance with the closest threshold value to the desired target
    `static void` | `main(java.lang.String[] args)` Tests the ThresholdCurve generation from the command line.

    - ### Methods inherited from class java.lang.Object

      `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### RELATION_NAME

          public static final java.lang.String RELATION_NAME

      The name of the relation used in threshold curve datasets
      See Also:
        Constant Field Values

    - #### TRUE_POS_NAME

          public static final java.lang.String TRUE_POS_NAME

      attribute name: True Positives
      See Also:
        Constant Field Values

    - #### FALSE_NEG_NAME

          public static final java.lang.String FALSE_NEG_NAME

      attribute name: False Negatives
      See Also:
        Constant Field Values

    - #### FALSE_POS_NAME

          public static final java.lang.String FALSE_POS_NAME

      attribute name: False Positives
      See Also:
        Constant Field Values

    - #### TRUE_NEG_NAME

          public static final java.lang.String TRUE_NEG_NAME

      attribute name: True Negatives
      See Also:
        Constant Field Values

    - #### FP_RATE_NAME

          public static final java.lang.String FP_RATE_NAME

      attribute name: False Positive Rate"
      See Also:
        Constant Field Values

    - #### TP_RATE_NAME

          public static final java.lang.String TP_RATE_NAME

      attribute name: True Positive Rate
      See Also:
        Constant Field Values

    - #### PRECISION_NAME

          public static final java.lang.String PRECISION_NAME

      attribute name: Precision
      See Also:
        Constant Field Values

    - #### RECALL_NAME

          public static final java.lang.String RECALL_NAME

      attribute name: Recall
      See Also:
        Constant Field Values

    - #### FALLOUT_NAME

          public static final java.lang.String FALLOUT_NAME

      attribute name: Fallout
      See Also:
        Constant Field Values

    - #### FMEASURE_NAME

          public static final java.lang.String FMEASURE_NAME

      attribute name: FMeasure
      See Also:
        Constant Field Values

    - #### SAMPLE_SIZE_NAME

          public static final java.lang.String SAMPLE_SIZE_NAME

      attribute name: Sample Size
      See Also:
        Constant Field Values

    - #### LIFT_NAME

          public static final java.lang.String LIFT_NAME

      attribute name: Lift
      See Also:
        Constant Field Values

    - #### THRESHOLD_NAME

          public static final java.lang.String THRESHOLD_NAME

      attribute name: Threshold
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### ThresholdCurve

          public ThresholdCurve()

  - ### Method Detail

    - #### getCurve

          public Instances getCurve(java.util.ArrayList<Prediction> predictions)

      Calculates the performance stats for the default class and return results as a set of Instances. The structure of these Instances is as follows:

      - True Positives
      - False Negatives
      - False Positives
      - True Negatives
      - False Positive Rate
      - True Positive Rate
      - Precision
      - Recall
      - Fallout
      - Threshold contains the probability threshold that gives rise to the previous performance values.

      For the definitions of these measures, see TwoClassStats

      Parameters:
        `predictions` - the predictions to base the curve on
      Returns:
        datapoints as a set of instances, null if no predictions have been made.
      See Also:
        `TwoClassStats`

    - #### getCurve

          public Instances getCurve(java.util.ArrayList<Prediction> predictions,
                           int classIndex)

      Calculates the performance stats for the desired class and return results as a set of Instances.
      Parameters:
        `predictions` - the predictions to base the curve on
        `classIndex` - index of the class of interest.
      Returns:
        datapoints as a set of instances.

    - #### getNPointPrecision

          public static double getNPointPrecision(Instances tcurve,
                                  int n)

      Calculates the n point precision result, which is the precision averaged over n evenly spaced (w.r.t recall) samples of the curve.
      Parameters:
        `tcurve` - a previously extracted threshold curve Instances.
        `n` - the number of points to average over.
      Returns:
        the n-point precision.

    - #### getPRCArea

          public static double getPRCArea(Instances tcurve)

      Calculates the area under the precision-recall curve (AUPRC).
      Parameters:
        `tcurve` - a previously extracted threshold curve Instances.
      Returns:
        the PRC area, or Double.NaN if you don't pass in a ThresholdCurve generated Instances.

    - #### getROCArea

          public static double getROCArea(Instances tcurve)

      Calculates the area under the ROC curve as the Wilcoxon-Mann-Whitney statistic.
      Parameters:
        `tcurve` - a previously extracted threshold curve Instances.
      Returns:
        the ROC area, or Double.NaN if you don't pass in a ThresholdCurve generated Instances.

    - #### getThresholdInstance

          public static int getThresholdInstance(Instances tcurve,
                                 double threshold)

      Gets the index of the instance with the closest threshold value to the desired target
      Parameters:
        `tcurve` - a set of instances that have been generated by this class
        `threshold` - the target threshold
      Returns:
        the index of the instance that has threshold closest to the target, or -1 if this could not be found (i.e. no data, or bad threshold target)

    - #### getRevision

          public java.lang.String getRevision()

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

    - #### main

          public static void main(java.lang.String[] args)

      Tests the ThresholdCurve generation from the command line. The classifier is currently hardcoded. Pipe in an arff file.
      Parameters:
        `args` - currently ignored