#! /usr/bin/env python
#
def vandermonde_value_1d ( nd, cd, ni, xi ):

#*****************************************************************************80
#
## VANDERMONDE_VALUE_1D evaluates a Vandermonde interpolant.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    03 July 2015
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer ND, the number of data values.
#
#    Input, real CD(ND,1), the polynomial coefficients.  
#    CD(I) is the coefficient of X^(I-1).
#
#    Input, integer NI, the number of interpolation points.
#
#    Input, real XI(NI,1), the interpolation points.
#
#    Output, real YI(NI,1), the interpolation values.
#
  import numpy as np

  yi = np.zeros ( ni )

  for j in range ( 0, ni ):
    yi[j] = cd[nd-1]
    for i in range ( nd - 2, -1, -1 ):
      yi[j] = yi[j] * xi[j] + cd[i]

  return yi

def vandermonde_value_1d_test ( ):

#*****************************************************************************80
#
## VANDERMONDE_VALUE_1D_TEST tests VANDERMONDE_VALUE_1D.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    03 July 2015
#
#  Author:
#
#    John Burkardt
#
  import numpy as np
  import platform
  from r8poly_print import r8poly_print
  from r8vec2_print import r8vec2_print

  print ( '' )
  print ( 'VANDERMONDE_VALUE_1D_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  VANDERMONDE_VALUE_1D evaluates a Vandermonde interpolant.' )

  nd = 5
  cd = np.array ( [ 24.0, -50.0, +35.0, -10.0, 1.0 ] )
  r8poly_print ( nd - 1, cd, '  The Vandermonde interpolant:' )

  ni = 16
  x_lo = 0.0
  x_hi = 5.0
  xi = np.linspace ( x_lo, x_hi, ni )

  yi = vandermonde_value_1d ( nd, cd, ni, xi )

  r8vec2_print ( ni, xi, yi, '  Vandermonde interpolant values:' )
#
#  Terminate.
#
  print ( '' )
  print ( 'VANDERMONDE_VALUE_1D_TEST:' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  vandermonde_value_1d_test ( )
  timestamp ( )