Linear Operators (sigpy.linop)

This module contains an abstraction class Linop for linear operators, and provides commonly used linear operators, including signal transforms such as FFT, NUFFT, and wavelet, and array manipulation operators, such as reshape, transpose, and resize.

The Linear Operator Class

sigpy.linop.Linop Abstraction for linear operator.

Linop Manipulation

The following are classes that take in Linops and compose them to form a new Linop.

sigpy.linop.Conj Complex conjugate of linear operator.
sigpy.linop.Add Addition of linear operators.
sigpy.linop.Compose Composition of linear operators.
sigpy.linop.Hstack Horizontally stack linear operators.
sigpy.linop.Vstack Vertically stack linear operators.
sigpy.linop.Diag Diagonally stack linear operators.

Basic Linops

sigpy.linop.Embed Embed input into a zero array with the given shape and index.
sigpy.linop.Identity Identity linear operator.
sigpy.linop.Reshape Reshape input to given output shape.
sigpy.linop.Slice Slice input with given index.
sigpy.linop.Transpose Tranpose input with the given axes.

Convolution Linops

sigpy.linop.ConvolveData Convolution operator for data arrays.
sigpy.linop.ConvolveDataAdjoint Adjoint convolution operator for data arrays.
sigpy.linop.ConvolveFilter Convolution operator for filter arrays.
sigpy.linop.ConvolveFilterAdjoint Adjoint convolution operator for filter arrays.

Fourier Linops

sigpy.linop.FFT FFT linear operator.
sigpy.linop.IFFT IFFT linear operator.
sigpy.linop.NUFFT NUFFT linear operator.
sigpy.linop.NUFFTAdjoint NUFFT adjoint linear operator.

Multiplication Linops

sigpy.linop.MatMul Matrix multiplication.
sigpy.linop.RightMatMul Matrix multiplication on the right.
sigpy.linop.Multiply Multiplication linear operator.

Interapolation Linops

sigpy.linop.Interpolate Interpolation linear operator.
sigpy.linop.Gridding Gridding linear operator.

Array Manipulation Linops

sigpy.linop.Resize Resize linear operator.
sigpy.linop.Flip Flip linear operator.
sigpy.linop.Downsample Downsampling linear operator.
sigpy.linop.Upsample Upsampling linear operator.
sigpy.linop.Circshift Circular shift linear operator.
sigpy.linop.Sum Sum linear operator.
sigpy.linop.Tile Tile linear operator.
sigpy.linop.FiniteDifference Linear operator that computes finite difference gradient.

Wavelet Transform Linops

sigpy.linop.Wavelet Wavelet transform linear operator.
sigpy.linop.InverseWavelet Inverse wavelet transform linear operator.

Block Reshape Linops

sigpy.linop.ArrayToBlocks Extract blocks from an array in a sliding window manner.
sigpy.linop.BlocksToArray Accumulate blocks into an array in a sliding window manner.