The Jaccard index between two sets is defined as the size of the intersection of
the sets divided by the size of the union. The Jaccard distance is simply 1 minus the Jaccard index.
The Jaccard distance between two genomes describes their degree of overlap with respect to gene
cluster content. If the Jaccard distance is 0.0, the two genomes contain identical gene clusters.
If it is 1.0 the two genomes are non-overlapping. The difference between a genomic fluidity (see
fluidity
) and a Jaccard distance is small, they both measure overlap between genomes,
but fluidity is computed for the population by averaging over many pairs, while Jaccard distances are
computed for every pair. Note that only presence/absence of gene clusters are considered, not multiple
occurrences.
The input pan.matrix is typically constructed by panMatrix
.