Colin - 3 months ago 136

Python Question

`import numpy as np`

def qrhouse(A):

(m,n) = A.shape

R = A

V = np.zeros((m,n))

for k in range(0,min(m-1,n)):

x = R[k:m,k]

x.shape = (m-k,1)

v = x + np.sin(x[0])*np.linalg.norm(x.T)*np.eye(m-k,1)

V[k:m,k] = v

R[k:m,k:n] = R[k:m,k:n]-(2*v)*(np.transpose(v)*R[k:m,k:n])/(np.transpose(v)*v)

R = np.triu(R[0:n,0:n])

return V, R

A = np.array( [[1,1,2],[4,3,1],[1,6,6]] )

print qrhouse(A)

It's qr factorization pytho code I don't know why error happens...

value error happens in

`V[k:m,k] = v`

`value error :`

could not broadcast input array from shape (3,1) into shape (3)

.

Answer

`V[k:m,k] = v`

; `v`

has shape (3,1), but the target is (3,). `k:m`

is a 3 term slice; `k`

is a scalar.

Try using `v.ravel()`

. Or `V[k:m,[k]]`

.

But also understand why `v`

has its shape.