Measure to compare two or more sets w.r.t. their similarity.

## Details

For two sets $$A$$ and $$B$$, the Jaccard Index is defined as $$J(A, B) = \frac{|A \cap B|}{|A \cup B|}.$$ If more than two sets are provided, the mean of all pairwise scores is calculated.

This measure is undefined if two or more sets are empty.

## Note

This measure requires learners with property "selected_features". The extracted feature sets are passed to mlr3measures::jaccard() from package mlr3measures.

If the measure is undefined for the input, NaN is returned. This can be customized by setting the field na_value.

## Dictionary

This Measure can be instantiated via the dictionary mlr_measures or with the associated sugar function msr():

mlr_measures\$get("sim.jaccard")
msr("sim.jaccard")

## Meta Information

• Type: "similarity"

• Range: $$[0, 1]$$

• Minimize: FALSE

as.data.table(mlr_measures) for a complete table of all (also dynamically created) Measure implementations.
Other similarity measures: mlr_measures_sim.phi