Fitch's Algorithm

Counting Mutations

Every union event in the Fitch pass contributes one mutation.

highlighted = computed this step

Each union event counts one mutation

When child sets do not intersect, Fitch takes their union and adds one mutation to the score.

union event⇒+1\text{union event} \Rightarrow +1
Counting union eventsEach union event contributes one mutation to the score.NodeUnion?Running count0no01no02yes13no14no15yes26no2

The total is the parsimony score

There are 2 union events, so the parsimony score is 2.

score=2\text{score}=2
Counting union eventsEach union event contributes one mutation to the score.NodeUnion?Running count0no01no02yes13no14no15yes26no2