The center2interval command finds ranges of values determined
by their centers.
center2interval
takes one mandatory argument and one optional argument:
L, a list of real numbers.
Optionally, c, a real number (by default
L[0]−(L[1]−L[0])/2).
center2interval(L ⟨,c⟩) returns a
list of ranges of values; the midpoints of the elements of the lists
are endpoints of the ranges; so, for example, the second range will
go from (L[0]+L[1])/2 to (L[1]+L[2])/2, etc. By default the
first and last range are centered on L[0] and L[−1]. With an
argument of c, however, the first range will begin at c.
