Table Of Contents

VertexFrame classification_metrics

classification_metrics(self, label_column, pred_column, pos_label=None, beta=None, frequency_column=None)

Model statistics of accuracy, precision, and others.

Parameters:

label_column : unicode

The name of the column containing the correct label for each instance.

pred_column : unicode

The name of the column containing the predicted label for each instance.

pos_label : None (default=None)

beta : float64 (default=None)

This is the beta value to use for F_{ \beta} measure (default F1 measure is computed); must be greater than zero. Defaults is 1.

frequency_column : unicode (default=None)

The name of an optional column containing the frequency of observations.
Returns:

: dict

The data returned is composed of multiple components:

<object>.accuracy : double
<object>.confusion_matrix : table
<object>.f_measure : double
<object>.precision : double
<object>.recall : double

Calculate the accuracy, precision, confusion_matrix, recall and F_{ \beta} measure for a classification model.

  • The f_measure result is the F_{ \beta} measure for a classification model. The F_{ \beta} measure of a binary classification model is the harmonic mean of precision and recall. If we let:

    • beta \equiv \beta,
    • T_{P} denotes the number of true positives,
    • F_{P} denotes the number of false positives, and
    • F_{N} denotes the number of false negatives

    then:

    F_{ \beta} = (1 + \beta ^ 2) * \frac{ \frac{T_{P}}{T_{P} + F_{P}} * \ \frac{T_{P}}{T_{P} + F_{N}}}{ \beta ^ 2 * \frac{T_{P}}{T_{P} + \ F_{P}} + \frac{T_{P}}{T_{P} + F_{N}}}

    The F_{ \beta} measure for a multi-class classification model is computed as the weighted average of the F_{ \beta} measure for each label, where the weight is the number of instances of each label. The determination of binary vs. multi-class is automatically inferred from the data.

  • The recall result of a binary classification model is the proportion of positive instances that are correctly identified. If we let T_{P} denote the number of true positives and F_{N} denote the number of false negatives, then the model recall is given by \frac {T_{P}} {T_{P} + F_{N}}.

    For multi-class classification models, the recall measure is computed as the weighted average of the recall for each label, where the weight is the number of instances of each label. The determination of binary vs. multi-class is automatically inferred from the data.

  • The precision of a binary classification model is the proportion of predicted positive instances that are correctly identified. If we let T_{P} denote the number of true positives and F_{P} denote the number of false positives, then the model precision is given by: \frac {T_{P}} {T_{P} + F_{P}}.

    For multi-class classification models, the precision measure is computed as the weighted average of the precision for each label, where the weight is the number of instances of each label. The determination of binary vs. multi-class is automatically inferred from the data.

  • The accuracy of a classification model is the proportion of predictions that are correctly identified. If we let T_{P} denote the number of true positives, T_{N} denote the number of true negatives, and K denote the total number of classified instances, then the model accuracy is given by: \frac{T_{P} + T_{N}}{K}.

    This measure applies to binary and multi-class classifiers.

  • The confusion_matrix result is a confusion matrix for a binary classifier model, formatted for human readability.

Notes

The confusion_matrix is not yet implemented for multi-class classifiers.

Examples

Consider Frame my_frame, which contains the data

>>> my_frame.inspect()
[#]  a      b  labels  predictions
==================================
[0]  red    1       0            0
[1]  blue   3       1            0
[2]  green  1       0            0
[3]  green  0       1            1

>>> cm = my_frame.classification_metrics('labels', 'predictions', 1, 1)
[===Job Progress===]

>>> cm.f_measure
0.6666666666666666

>>> cm.recall
0.5

>>> cm.accuracy
0.75

>>> cm.precision
1.0

>>> cm.confusion_matrix
            Predicted_Pos  Predicted_Neg
Actual_Pos              1              1
Actual_Neg              0              2
  • © Copyright 2015, Intel.
  • Last updated on Jan 08, 2016.