Python 检查矩阵在Numpy中是否对称
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Checking if a matrix is symmetric in Numpy
提问by plshalp
I'm trying to make a function with the arguments (a,tol=1e-8)that returns a boolean value that tells the user whether or not the matrix is symmetric (symmetric matrix is equal to its transpose). So far I have:
我正在尝试使用(a,tol=1e-8)返回一个布尔值的参数创建一个函数，该值告诉用户矩阵是否对称（对称矩阵等于其转置）。到目前为止，我有：
def check_symmetric(a, tol=1e-8):
if np.transpose(a, axes=axes) == np.transpose(a, axes=axes):
return True
def sqr(s):
rows = len(s)
for row in sq:
if len(row) != rows:
return False
return True
if a != sqr(s):
raise ValueError
although I keep getting an axes isn't definedmessage so I'm pretty sure that doesn't work at all...... the tests I'd like to pass are:
虽然我不断收到一条axes isn't defined消息，所以我很确定这根本不起作用......我想通过的测试是：
e = np.eye(4)
f = np.diag([1], k=3)
g = e[1:, :]
print(check_symmetric(e))
print(not check_symmetric(e + f))
print(check_symmetric(e + f * 1e-9))
print(not check_symmetric(e + f * 1e-9, 1e-10))
try:
check_symmetric(g)
print(False)
except ValueError:
print(True)
Any help is appreciated, thanks!
任何帮助表示赞赏，谢谢！
回答by Nils Werner
You can simply compare it to its transpose using allclose
您可以简单地将它与它的转置进行比较 allclose
def check_symmetric(a, rtol=1e-05, atol=1e-08):
return numpy.allclose(a, a.T, rtol=rtol, atol=atol)
回答by Andrés Marulanda
The following function also solves the problem:
下面的函数也解决了这个问题：
def check_symmetric(a, tol=1e-8):
return np.all(np.abs(a-a.T) < tol)
