materials

fftfreq.py
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			from __future__ import division

			__author__ = "Lucas Frérot"

			import numpy as np
			from numpy.fft import fftfreq


			def frequencies1D(frequencies):
			n = len(frequencies)
			frequencies[:] = n * fftfreq(n)


			def assign2DFrequencies(qx, qy, frequencies):
			qx, qy = np.meshgrid(qx, qy, indexing='ij')

			frequencies[:, :, 0] = qx
			frequencies[:, :, 1] = qy


			def frequencies2D(frequencies):
			n = frequencies.shape
			qx = fftfreq(n[0]) * n[0]
			qy = fftfreq(n[1]) * n[1]
			assign2DFrequencies(qx, qy, frequencies)


			def hfrequencies2D(frequencies):
			n = frequencies.shape
			qx = fftfreq(n[0]) * n[0]
			qy = np.arange(n[1])
			assign2DFrequencies(qx, qy, frequencies)