def kron(a,b):
"""kronecker product of a and b
Kronecker product of two matrices is block matrix
[[ a[ 0 ,0]*b, a[ 0 ,1]*b, ... , a[ 0 ,n-1]*b ],
[ ... ... ],
[ a[m-1,0]*b, a[m-1,1]*b, ... , a[m-1,n-1]*b ]]
"""
if not a.iscontiguous():
a = reshape(a, a.shape)
if not b.iscontiguous():
b = reshape(b, b.shape)
o = outerproduct(a,b)
o.shape = a.shape + b.shape
return concatenate(concatenate(o, axis=1), axis=1)
def ifftshift(x,axes=None):
""" ifftshift(x,axes=None) - > y
Inverse of fftshift.
"""
tmp = asarray(x)
ndim = len(tmp.shape)
if axes is None:
axes = range(ndim)
y = tmp
for k in axes:
n = tmp.shape[k]
p2 = n-(n+1)/2
mylist = concatenate((arange(p2,n),arange(p2)))
y = take(y,mylist,k)
return y
def fftshift(x,axes=None):
""" fftshift(x, axes=None) -> y
Shift zero-frequency component to center of spectrum.
This function swaps half-spaces for all axes listed (defaults to all).
Notes:
If len(x) is even then the Nyquist component is y[0].
"""
tmp = asarray(x)
ndim = len(tmp.shape)
if axes is None:
axes = range(ndim)
y = tmp
for k in axes:
n = tmp.shape[k]
p2 = (n+1)/2
mylist = concatenate((arange(p2,n),arange(p2)))
y = take(y,mylist,k)
return y
