[英]TypeError: 'dia_matrix' object has no attribute '__getitem__' - Python
I'm currently trying to dot product a row from a diagonal matrix formed by scipy.sparse.diags function in "Poisson Stiffness" below, but i am having trouble selecting the row and am getting the following error: 我目前正在尝试从下面的“泊松刚度”中scipy.sparse.diags函数形成的对角矩阵中点积一行,但是我在选择该行时遇到了麻烦,并且遇到了以下错误:
TypeError: 'dia_matrix' object has no attribute '__getitem__'
The following is my code 以下是我的代码
def Poisson_Stiffness(x0):
"""Finds the Poisson equation stiffness matrix with any non uniform mesh x0"""
x0 = np.array(x0)
N = len(x0) - 1 # The amount of elements; x0, x1, ..., xN
h = x0[1:] - x0[:-1]
a = np.zeros(N+1)
a[0] = 1 #BOUNDARY CONDITIONS
a[1:-1] = 1/h[1:] + 1/h[:-1]
a[-1] = 1/h[-1]
a[N] = 1 #BOUNDARY CONDITIONS
b = -1/h
b[0] = 0 #BOUNDARY CONDITIONS
c = -1/h
c[N-1] = 0 #BOUNDARY CONDITIONS: DIRICHLET
data = [a.tolist(), b.tolist(), c.tolist()]
Positions = [0, 1, -1]
Stiffness_Matrix = diags(data, Positions, (N+1,N+1))
return Stiffness_Matrix
def Error_Indicators(Uh,U_mesh,Z,Z_mesh,f):
"""Take in U, Interpolate to same mesh as Z then solve for eta"""
u_inter = interp1d(U_mesh,Uh) #Interpolation of old mesh
U2 = u_inter(Z_mesh) #New function u for the new mesh to use in
Bz = Poisson_Stiffness(Z_mesh)
eta = np.empty(len(Z_mesh))
for i in range(len(Z_mesh)):
eta[i] = (f[i] - np.dot(Bz[i,:],U2[:]))*z[i]
return eta
The error is specifically coming from the following line of code: 该错误专门来自以下代码行:
eta[i] = (f[i] - np.dot(Bz[i,:],U2[:]))*z[i]
It is the Bz matrix that is causing the error, being created using scipy.sparse.diags and will not allow me to call the row. 使用scipy.sparse.diags创建的是导致错误的Bz矩阵,不允许我调用该行。
Bz = Poisson_Stiffness(np.linspace(0,1,40))
print Bz[0,0]
This code will also produce the same error. 此代码也将产生相同的错误。
Any help is very much appreciated Thanks 任何帮助都非常感谢
sparse.dia_matrix
apparently does not support indexing. sparse.dia_matrix
显然不支持索引。 The way around that would be to convert it to another format. 解决方法是将其转换为另一种格式。 For calculation purposes
tocsr()
would be appropriate. 出于计算目的,
tocsr()
是合适的。
The documentation for dia_matrix
is limited, though I think the code is visible Python. dia_matrix
的文档是有限的,尽管我认为代码是可见的Python。 I'd have to double check, but I think it is a matrix construction tool, not a fully developed working format. 我必须仔细检查,但我认为它是矩阵构造工具,而不是完全开发的工作格式。
In [97]: M=sparse.dia_matrix(np.ones((3,4)),[0,-1,2])
In [98]: M[1,:]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-98-a74bcb661a8d> in <module>()
----> 1 M[1,:]
TypeError: 'dia_matrix' object is not subscriptable
In [99]: M.tocsr()[1,:]
Out[99]:
<1x4 sparse matrix of type '<class 'numpy.float64'>'
with 4 stored elements in Compressed Sparse Row format>
A dia_matrix
stores its information in a .data
and .offsets
attributes, which are simple modifications of the input parameters. dia_matrix
将其信息存储在.data
和.offsets
属性中,这是对输入参数的简单修改。 They aren't ammenable for 2d indexing. 它们不适用于2d索引。
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