reposition is a helper function used for manually creating
"dendrogram" objects from nested lists. The function
recursively reassigns the 'height' attributes at each node by
a given constant.
Usage
reposition(x, shift = "reset")
Arguments
x
an object of class "dendrogram".
shift
either the character string "reset" (shift the graph so that
the height of the farthest leaf from the root is zero), or a numeric value
giving the amount to shift the graph along the primary axis.