Removes all tips that do not occur in both tree1 and tree2, then calculates the status of the remaining quartets.

PairSharedQuartetStatus(tree1, tree2)

## Arguments

tree1, tree2

Trees of class phylo to compare.

## Value

Returns a named array of six integers corresponding to the quantities of Estabrook et al. (1985):

N

The total number of quartet statements for two trees of n leaves, i.e. 2 Q.

Q

The total number of quartets for n leaves.

s

The number of quartets that are resolved identically in both trees.

d

The number of quartets that are resolved differently in each tree.

r1

The number of quartets that are resolved in tree 1, but not in tree 2.

r2

The number of quartets that are resolved in tree 2, but not in tree 1.

u

The number of quartets that are unresolved in both trees.

Other element-by-element comparisons: CompareQuartetsMulti(), CompareQuartets(), CompareSplits(), QuartetState(), SharedQuartetStatus(), SplitStatus()