Python中的 numpy.poly()

多项式根序列中的numpy.poly()函数返回多项式的系数。

Syntax :numpy.poly(seq)

Parameters :
Seq : sequence of roots of the polynomial roots, or a matrix of roots.

Return: 1D array having coefficients of the polynomial from the highest degree to the lowest one.
c[0] * x**(N) + c[1] * x**(N-1) + … + c[N-1] * x + c[N] where c[0] always equals 1.

# Python code explaining  
# numpy.poly() 
      
# importing libraries 
import numpy as np 
    
# Giving the roots 
seq_1 = (2, 1, 0)
a = np.poly(seq_1)
print ("Coefficients of the polynomial: ", a)
  
# Constructing polynomial  
p1 = np.poly1d(a)
print ("\nAbove polynomial = \n", p1) 

输出 ：

Coefficients of the polynomial:  [ 1. -3.  2.  0.]

Above polynomial = 
    3     2
1 x - 3 x + 2 x

代码#2：

# Python code explaining  
# numpy.poly() 
      
# importing libraries 
import numpy as np 
  
# Giving the roots
seq_2 = (2, 1, 0, 2, 4, 2)
b = np.poly(seq_2)
print ("Coefficients of the polynomial: ", b)
  
# Constructing polynomial  
p2 = np.poly1d(b)
print ("\nAbove polynomial = \n", p2) 

输出 ：

Coefficients of the polynomial:  [  1. -11.  46. -92.  88. -32.   0.]

Above polynomial = 
    6      5      4      3      2
1 x - 11 x + 46 x - 92 x + 88 x - 32 x