def enlarge(self, M):
"""
It enlarges a trigonometric polynomial by adding zeros to the Fourier
coefficients with high frequencies.
"""
if np.allclose(self.N, M):
return self
val = np.zeros(np.hstack([self.d, M]), dtype=self.val.dtype)
if self.Fourier is False:
for m in np.arange(self.d):
val[m] = enlargeF(self.val[m], M)
else:
for m in np.arange(self.d):
val[m] = enlarge(self.val[m], M)
return VecTri(name=self.name, val=val, Fourier=self.Fourier)
def enlargeF(xN, M):
"""
It enlarges an array of grid values. First, Fourier coefficients are
calculated and complemented by zeros. Then an inverse DFT provides
the grid values on required grid.
Parameters
----------
xN : numpy.ndarray of shape = N
input array that is to be enlarged
Returns
-------
xM : numpy.ndarray of shape = M
output array that is enlarged
M : array like
number of grid points
"""
N = np.array(np.shape(xN))
M = np.array(M, dtype=np.int32)
FxM = enlarge(DFT.fftnc(xN, N)*np.float(np.prod(M))/np.prod(N), M)
xM = np.real(DFT.ifftnc(FxM, M))
return xM