Included

Key Included in Intervaled Real Fn refers to a 1D-array of r - 1 integers, where r - 1 is the number of elements specified in Nodes
If its iᵗʰ element is non-zero, then the corresponding node dᵢ is part of the interval that ends at that node.
Otherwise (the zero case), the previous statement does not hold and the corresponding node dᵢ is part of the interval that starts at that node.
It may be omitted, in which case it is set internally to hold zero values.