我正在尝试实现用于数值评估矩阵特征值的幂方法,这是代码:
A = matrix(c(1, 1, 2, 0), 2, 2, byrow=TRUE)
x0 = c(1, 0)
powerm = function(A, x0, thresh)
{
m0 = max(x0)
x1 = A %*% (x0 / m0)
m1 = max(x1)
if(abs(m1 - m0) < thresh)
{
return(m1)
}
else
{
powerm(A, x1, thresh)
}
}
ev1 = powerm(A, x0, 1e-4)
ev2 = powerm(A - diag(2)*ev1, x0, 1e-4)
此函数毫无问题地获取第一个特征值,但在获取第二个时失败(参见代码的最后一行)。你能帮我找出原因吗?谢谢。
我还用python重写了它:
import numpy as np
A = np.matrix([[1, 1], [2, 0]])
x0 = np.matrix([1, 0]).reshape(2, 1)
def powerm(A, x0, thresh):
m0 = x0.max()
x1 = A * (x0 / m0)
m1 = x1.max()
if abs(m1 - m0) < thresh:
return m1
else:
return powerm(A, x1, thresh)
ev1 = powerm(A, x0, 1e-12)
A1 = A - np.identity(2) * ev1
ev2 = powerm(A1, x0, 1e-12)
我收到以下错误:
AttributeError: 'numpy.ndarray' object has no attribute '_collapse'