def self_isf(self,start,stop,av):
"""
Self intermediate scattering function
If av is 0 (Default), the calculation will act greedily,
averaging over all the avilabe intervals of a given length.
Example : start=1 stop=4 av=0
ISF[0] = 1
ISF[1] = ( isf([1,2]) + isf([2,3]) + isf([3,4]))/3
ISF[2] = ( isf([1,3]) + isf([2,4]) )/2
ISF[3] = isf([1,4])
If av>0, the average will be done over av time intervals starting
from start, start+1,...,start+av-1
Example : start=1 stop=4 av=2
ISF[0] = 1
ISF[1] = ( isf([1,2]) + isf([2,3]) )/2
ISF[2] = ( isf([1,3]) + isf([2,4]) )/2
ISF[3] = ( isf([1,4]) + isf([2,5]) )/2
"""
A = numexpr.evaluate('exp(r * q)',{
'r':self.positions[start:stop+av-1],
'q': (1j * np.pi / self.xp.radius)}
)
return statistics.time_correlation(A, av).mean(axis=-1).real
def self_isf(positions, radius, av, L=203):
"""Self intermediate scattering function in a cubic periodic box"""
A = np.exp(
positions * (1j * np.pi * np.floor(L/radius) / L)
)
return statistics.time_correlation(A, av).mean(axis=-1).real
def self_isf(positions, radius, av, L=203):
"""Self intermediate scattering function in a cubic periodic box"""
A = np.exp(positions * (1j * np.pi * np.floor(L / radius) / L))
return statistics.time_correlation(A, av).mean(axis=-1).real