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TravelSignal: extract time_offset into method

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Eric Teunis de Boone 2022-03-10 17:07:22 +01:00
parent c4382f3eb2
commit f5f2cc9b18
1 changed files with 58 additions and 37 deletions
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91
simulations/lib/travelsignal.py
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@ -11,7 +11,7 @@ class TravelSignal:
Model an arbitrary digitised signal that can be translated to another position and time.
"""
def __init__(self, signal, sample_rate, t_0 = 0, x_0 = 0, periodic=True, interp1d_kw = None):
def __init__(self, signal, sample_rate, t_0 = 0, x_0 = 0, periodic=True, interp1d_kw = None, velocity=None):
"""
Initialise by saving the raw signal
@ -32,17 +32,21 @@ class TravelSignal:
Use scipy.interpolate's interp1d_kw for interpolation.
Set to True, or a dictionary to enable.
Dictionary will be entered in as **kwargs.
velocity : float, optional
Defaults to the speed of light in m/s.
"""
self.raw = signal
self.raw = np.asarray(signal)
self.periodic = periodic
self.sample_rate = sample_rate # Hz
self.sample_length = len(self.raw)
self.time_length = self.sample_length*sample_rate # s
self.x_0 = x_0
self.t_0 = t_0
self.velocity = 299792458 if velocity is None else velocity # m / s
self.x_0 = x_0 # m
self.t_0 = t_0 # s
# choose interpolation method
if not interp1d_kw:
@ -87,36 +91,7 @@ class TravelSignal:
Returns the signal at (t_f, x_f)
"""
if t_0 is None:
t_0 = self.t_0
if velocity is None:
velocity = 1
## spatial offset
if x_f is None:
spatial_time_offset = 0
else:
x_f = np.asarray(x_f)
if x_0 is None:
x_0 = self.x_0
spatial_time_offset = np.sum(np.sqrt( (x_f - x_0)**2 )/velocity)
## temporal offset
if t_f is None:
temporal_time_offset = 0
else:
t_f = np.asarray(t_f)
if t_0 is None:
t_0 = self.t_0
temporal_time_offset = t_f - t_0
# total offset
total_time_offset = temporal_time_offset - spatial_time_offset
total_time_offset = self.total_time_offset(t_f=t_f, x_f=x_f, t_0=t_0, x_0=x_0, velocity=velocity)
n_offset = (total_time_offset * self.sample_rate )
# periodic signal
@ -169,6 +144,52 @@ class TravelSignal:
return amplitude, total_time_offset
def spatial_time(self, x_f, velocity=None, x_0=None):
"""
Calculate the time offset caused by a spatial difference.
"""
if velocity is None:
velocity = self.velocity
if x_0 is None:
x_0 = self.x_0
return np.sum(np.sqrt( (x_f - x_0)**2 )/velocity)
def total_time_offset(self, t_f = None, x_f = None, t_0 = None, x_0 = None, velocity = None):
"""
Calculate how much time shifting is needed to go from (t_0, x_0) to (t_f, x_f).
Convention:
(t_0, x_0) < (t_f, x_0) gives a positive time shift,
(t_0, x_0) != (t_0, x_f) gives a negative time shift
Returns:
the time shift
"""
## spatial offset
if x_f is None:
spatial_time_offset = 0
else:
x_f = np.asarray(x_f)
if x_0 is None:
x_0 = self.x_0
spatial_time_offset = self.spatial_time(x_f, x_0=x_0, velocity=velocity)
## temporal offset
if t_f is None:
temporal_time_offset = 0
else:
t_f = np.asarray(t_f)
if t_0 is None:
t_0 = self.t_0
temporal_time_offset = t_f - t_0
return temporal_time_offset - spatial_time_offset
if __name__ == "__main__":
import matplotlib.pyplot as plt
@ -193,7 +214,7 @@ if __name__ == "__main__":
ax.set_xlabel("Time")
ax.plot(time, signal, label='Raw signal')
ax.plot(time2, mysignal(time2)+0.5, '.-', label='TravelSignal(periodic)+0.5')
ax.plot(time2, mysignal(time2) +0.5, '.-', label='TravelSignal(periodic)+0.5')
ax.plot(time2, mysignal2(time2)-0.5, '.-', label='TravelSignal-0.5')
ax.legend()