NB.  The essential five functions for Sample Calculus
NB.  ------------------------------------------------
	sample =: ,@({.@] + (%~ (}. -})) */ (i.@(1: + [)))
	d =:  }. - }
	mids =:  -: @ }. + }:
	S =: 0: , +/\
	sum =:  +/
A plot function is supplied with J4.05 and is accessible with:
	load 'plot'
It may also be convenient to
	load 'trig numeric'
and to define the verbs
	vs =:  ;~
	and=:  ,.
NB.  ------------------------------------------------
NB.  the first three of which could have been defined using:
NB.    first =.  {.   
NB.    of =.  @   
NB.    right =.  ]   
NB.    left =.  [   
NB.    h =.  %~ d   
NB.    indices=.  i. of (1: + left)  
NB.    half =.  -:   
NB.    behead =.  }.   
NB.    curtail =.  }:   
NB.    list=.  ,
NB. with:
NB.    sample=. list of ((first of right) + h */ indices)
NB.    d =. behead - curtail
NB.    mids =. half of (behead + curtail)
NB.-----------------------------------------------------------