#function [y] = Lagrange_interp_poly_val(a,x) # Accompanying program for the text # # Classical and Modern Numerical Analysis: # Theory, Methods and Practice # by Azmy S. Ackleh, Edward J. Allen, # R. Baker Kearfott, and Padmanabhan Seshaiyer # # (Taylor and Francis / CRC Press, 2009) # # [y] = Lagrange_interp_poly_val(a,x) # # returns the value of the Lagrange interpolating polynomial with # coefficients a (computed by Lagrange_interp_poly_coeffs.m) in y. # If x is a vector, then, upon return, y will contain the vector of # evaluations of Runge's function at corresponding components of x. # In such a case, y will be a row vector if x is a row vector, and y will # be a column vector if x is a column vector. def Lagrange_interp_poly_val(a,x): n = a.shape[0] y = a[0] for i in range(1,n): y += a[i]*x**i return y