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

## Details

The Phi Coefficient is defined as the Pearson correlation between the binary representation of two sets $$A$$ and $$B$$. The binary representation for $$A$$ is a logical vector of length $$p$$ with the i-th element being 1 if the corresponding element is in $$A$$, and 0 otherwise.

If more than two sets are provided, the mean of all pairwise scores is calculated.

This measure is undefined if one set contains none or all possible elements.

## Note

This measure requires learners with property "selected_features". The extracted feature sets are passed to mlr3measures::phi() 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.phi")
msr("sim.phi")

## Meta Information

• Type: "similarity"

• Range: $$[-1, 1]$$

• Minimize: FALSE

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