nltk.metrics.f_measure

nltk.metrics.f_measure(reference, test, alpha=0.5)

Given a set of reference values and a set of test values, return the f-measure of the test values, when compared against the reference values. The f-measure is the harmonic mean of the precision and recall, weighted by alpha. In particular, given the precision p and recall r defined by:

• p = card(reference intersection test)/card(test)

• r = card(reference intersection test)/card(reference)

The f-measure is:

• 1/(alpha/p + (1-alpha)/r)

If either reference or test is empty, then f_measure returns None.

Parameters

• reference (set) – A set of reference values.

• test (set) – A set of values to compare against the reference set.

Return type

float or None