scipy.signal.

czt_points

scipy.signal.czt_points(m, w=None, a=1 + 0j)

Return the points at which the chirp z-transform is computed.

Parameters:

mint

The number of points desired.

wcomplex, optional

The ratio between points in each step. Defaults to equally spaced points around the entire unit circle.

acomplex, optional

The starting point in the complex plane. Default is 1+0j.

Returns:

outndarray

The points in the Z plane at which CZT samples the z-transform, when called with arguments m, w, and a, as complex numbers.

See also

CZT

Class that creates a callable chirp z-transform function.

czt

Convenience function for quickly calculating CZT.

Notes

Array API Standard Support

czt_points has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable SCIPY_ARRAY_API=1 and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

Library	CPU	GPU
NumPy	✅	n/a
CuPy	n/a	⛔
PyTorch	⛔	⛔
JAX	⛔	⛔
Dask	⛔	n/a

See Support for the array API standard for more information.

Examples

Try it in your browser!

Plot the points of a 16-point FFT:

>>> import numpy as np
>>> from scipy.signal import czt_points
>>> points = czt_points(16)
>>> import matplotlib.pyplot as plt
>>> plt.plot(points.real, points.imag, 'o')
>>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
>>> plt.axis('equal')
>>> plt.show()

and a 91-point logarithmic spiral that crosses the unit circle:

>>> m, w, a = 91, 0.995*np.exp(-1j*np.pi*.05), 0.8*np.exp(1j*np.pi/6)
>>> points = czt_points(m, w, a)
>>> plt.plot(points.real, points.imag, 'o')
>>> plt.gca().add_patch(plt.Circle((0,0), radius=1, fill=False, alpha=.3))
>>> plt.axis('equal')
>>> plt.show()

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