python计算牛顿迭代多项式实例分析

''' p = evalPoly(a,xData,x).
 Evaluates Newton's polynomial p at x. The coefficient
 vector 'a' can be computed by the function 'coeffts'.
 a = coeffts(xData,yData).
 Computes the coefficients of Newton's polynomial.
''' 
def evalPoly(a,xData,x):
 n = len(xData) - 1 # Degree of polynomial
 p = a[n]
 for k in range(1,n+1):
 p = a[n-k] + (x -xData[n-k])*p
 return p
def coeffts(xData,yData):
 m = len(xData) # Number of data points
 a = yData.copy()
 for k in range(1,m):
 a[k:m] = (a[k:m] - a[k-1])/(xData[k:m] - xData[k-1])
 return a