desc.transform.Transform

class desc.transform.Transform(grid, basis, derivs=0, rcond='auto', build=True, build_pinv=False, method='auto')

Transforms from spectral coefficients to real space values.

Parameters:

• grid (Grid) – Collocation grid of real space coordinates

• basis (Basis) – Spectral basis of modes

• derivs (int or array-like) –

  • if an int, order of derivatives needed (default=0)

  • if an array, derivative orders specified explicitly. Shape should be (N,3), where each row is one set of partial derivatives [dr, dt, dz]

• rcond (float) – relative cutoff for singular values for inverse fitting

• build (bool) – whether to precompute the transforms now or do it later

• build_pinv (bool) – whether to precompute the pseudoinverse now or do it later

• method ({`'auto', ‘fft’`, 'direct1', 'direct2'}) –

  • 'fft' uses fast fourier transforms in the zeta direction, and so must have equally spaced toroidal nodes, and the same node pattern on each zeta plane

  • 'direct1' uses full matrices and can handle arbitrary node patterns and spectral bases.

  • 'direct2' uses a DFT instead of FFT that can be faster in practice

  • 'auto' selects the method based on the grid and basis resolution

Methods

build()	Build the transform matrices for each derivative order.
build_pinv()	Build the pseudoinverse for fitting.
change_derivatives(derivs[, build])	Change the order and updates the matrices accordingly.
change_resolution([grid, basis, build, ...])	Re-build the matrices with a new grid and basis.
copy([deepcopy])	Return a (deep)copy of this object.
eq(other)	Compare equivalence between DESC objects.
fit(x)	Transform from physical domain to spectral using weighted least squares fit.
load(load_from[, file_format])	Initialize from file.
project(y)	Project vector y onto basis.
save(file_name[, file_format, file_mode])	Save the object.
transform(c[, dr, dt, dz])	Transform from spectral domain to physical.

Attributes

basis	spectral basis for the transform.
built	whether the transform matrices have been built.
built_pinv	whether the pseudoinverse matrix has been built.
derivatives	Set of derivatives the transform can compute.
grid	collocation grid for the transform.
matrices	transform matrices such that x=A*c.
method	method of computing transform.
modes	spectral mode numbers.
nodes	collocation nodes.
num_modes	number of modes in the spectral basis.
num_nodes	number of nodes in the collocation grid.
rcond	reciprocal condition number for inverse transform.