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.

Examples

Plot the points of a 16-point FFT:

>>> 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()