# rderiv.py  uses deriv

from deriv import deriv
from nuderiv import nuderiv

def rderiv(order, npoints, point, h): # return c[]
  # compute coefficients to numerically compute 
  # a derivative  of order 'order' using 'npoints'               
  # at ordinate point,                                           
  # where order>=1, npoints>=order+1, 0 <= point < npoints,      
  # 'c' array returned with the coefficients,                    
  c  = [0.0 for i in range(npoints)]
  a  = [0.0 for i in range(npoints)]
  aa = [0.0 for i in range(npoints)]

  if(order+npoints<=15):
    a,bb = deriv(order, npoints, point)
    hpower = 1.0
    for i in range(order):
      hpower = hpower*h
        
    hpower = 1.0/(bb*hpower)
    for i in range(npoints):
      c[i]=hpower*a[i]

  else:
    for i in range(npoints):
      aa[i] = h*i
      
    c = nuderiv(order, npoints, point, aa)

  # end if
  return c

# end rderiv