def score(self, period):
"""Find the score for a given period."""
period = np.asarray(period)
# double-up the data to allow periodicity on the fits
N = len(self.t)
N4 = N // 4
t = np.concatenate([self.t, self.t])
y = np.concatenate([self.y, self.y])
dy = np.concatenate([self.dy, self.dy])
results = []
for p in period.ravel():
# compute doubled phase and sort
phase = t % p
phase[N:] += p
isort = np.argsort(phase)[N4:N + 3 * N4]
phase = phase[isort]
yp = y[isort]
dyp = dy[isort]
# compute model
model = ssm.SuperSmoother().fit(phase, yp, dyp, presorted=True)
# take middle residuals
resids = model.cv_residuals()[N4:N4 + N]
results.append(1 - np.mean(np.abs(resids)) / self.baseline_err)
return np.asarray(results).reshape(period.shape)
def _decompose_ssmoother(ts: t.Union[np.ndarray, pd.core.series.Series],
plot: bool = False) -> t.Tuple[np.ndarray, ...]:
"""Time-series decomposition using Friedman's Super Smoother.
The seasonal component returned is an array full of zeros with the same
length as the given time-series.
Parameters
----------
ts : :obj:`np.ndarray` or :obj:`pd.core.series.Series`
One-dimensional time-series values.
plot : bool, optional (default=False)
If True, plot the decomposed components.
Returns
-------
tuple of :obj:`np.ndarray`
A tuple with tree components, in the following order: time-series
trend component, an array full of zeros (seasonal component), and
the residual component.
References
----------
.. [1] Friedman, J. H. 1984, A variable span scatterplot smoother
Laboratory for Computational Statistics, Stanford University
Technical Report No. 5. Available at:
https://www.slac.stanford.edu/pubs/slacpubs/3250/slac-pub-3477.pdf
Accessed on May 12 2020.
"""
timestamp = np.arange(ts.size)
model = supersmoother.SuperSmoother().fit(timestamp, ts, presorted=True)
comp_trend = model.predict(timestamp)
comp_resid = ts - comp_trend
comp_season = np.zeros(ts.size, dtype=float)
if plot:
fig, (ax_raw, ax_trend, ax_resid) = plt.subplots(3, 1)
fig.suptitle("Friedman's Super Smoother results")
ax_raw.plot(ts)
ax_raw.set_title("Original time-series")
ax_trend.plot(comp_trend)
ax_trend.set_title("Trend component")
ax_resid.plot(comp_resid)
ax_resid.set_title("Residual component")
plt.show()
return comp_trend, comp_season, comp_resid
def __init__(self, x, y, name='SuperSmoother'):
tic = time.time()
if name == 'SuperSmoother':
min_J = 5 # min points in a window (otherwise no convergence). Does no work with less than 5!
s12 = 4 # multiplier from min to mid span, ie mid_span / min_span
s23 = 2.5 # multiplier from mid to max span, ie max_span / mid_span
# min data points: we must have min_J/len * s12 * s23 <= 1
min_len = min_J * s12 * s23
if len(y) < min_len:
print('ERROR: not enough data points: ' + str(len(y)) + '. Should be at least ' + str(min_len) + '. Try Lowess')
sys.exit(-1)
min_span = max(0.05, min_J / len(y))
self.model = sm.SuperSmoother(primary_spans=(min_span, min_span * s12, min_span * s12 * s23), middle_span=min_span * s12, final_span=min_span)
self.model.fit(x, y, dy=np.std(y))
elif name == 'Lowess':
self.model = LowessSmooth(x, y)
self.model.fit(x, y, dy=1.0) # get BW
else:
print('ERROR: invalid smoother: ' + str(name) + '. Valid smoothers are: SuperSmoother, Lowess')
sys.exit(-1)
def _score(self, periods):
return np.asarray([
1 -
(ssm.SuperSmoother(period=p).fit(self.t, self.y, self.dy).cv_error(
skip_endpoints=False) / self.baseline_err) for p in periods
])
def _predict(self, t, period):
model = ssm.SuperSmoother(period=period).fit(self.t, self.y, self.dy)
return model.predict(t)
def pre_whiten(time,
flux,
unc_flux,
period,
kind="supersmoother",
which="phased",
phaser=None):
"""Phase a lightcurve and then smooth it.
Inputs
------
time, flux, unc_flux: array_like
period: float
period to whiten by
kind: string, optional
type of smoothing to use. Defaults to "supersmoother."
Other types are "boxcar", "linear"
which: string, optional
whether to smooth the "phased" lightcurve (default) or the "full"
lightcurve.
phaser: Float, optional (default=None)
if kind="boxcar", phaser is the Half-width of the smoothing window.
if kind="supersmoother", phaser is alpha (the "bass enhancement").
Outputs
-------
white_flux, white_unc, smoothed_flux: arrays
"""
# print(which, period, phaser)
# phase the LC by the period
if period is not None:
# phased_time = utils.phase(time, period)
phased_time = (time % period)
else:
phased_time = time
if kind.lower() == "supersmoother":
if phaser is None:
logging.info("Phaser not set! "
"Set phaser=alpha (bass-enhancement value "
"for supersmoother) if desired.")
if which.lower() == "phased":
# Instantiate the supersmoother model object with the input period
model = supersmoother.SuperSmoother(period=period)
# Set up base arrays for phase for the fit
x_vals = np.linspace(0, max(phased_time) * 1.001, 1000)
# Run a fit for the y phase
y_fit = model.fit(phased_time, flux, unc_flux).predict(x_vals)
elif which.lower() == "full":
# Instantiate the supersmoother model object with the input period
model = supersmoother.SuperSmoother(alpha=phaser)
# Set up base arrays for time for the fit
x_vals = np.linspace(min(time), max(time), 1000)
# run a fit for the y values
y_fit = model.fit(time, flux, unc_flux).predict(x_vals)
else:
logging.warning("unknown which %s !!!", which)
elif kind.lower() == "boxcar":
if phaser is None:
logging.info("Phaser not set! "
"Set phaser to the width of the smoothing "
"box in pixels!")
if which.lower() == "phased":
# sort the phases
sort_locs = np.argsort(phased_time)
x_vals = phased_time[sort_locs]
flux_to_fit = flux[sort_locs]
elif which.lower() == "full":
x_vals = time
flux_to_fit = flux
else:
logging.warning("unknown which %s !!!", which)
# Use astropy's convolution function!
boxcar_kernel = convolution.Box1DKernel(width=phaser,
mode="linear_interp")
y_fit = convolution.convolve(flux_to_fit,
boxcar_kernel,
boundary="wrap")
elif kind == "linear":
if which != "full":
logging.warning("Linear smoothing only allowed for full "
"lightcurve! Switching to full mode.")
which = "full"
# Fit a line to the data
pars = np.polyfit(time, flux, deg=1)
m, b = pars
smoothed_flux = m * time + b
else:
logging.warning("unknown kind %s !!!", kind)
if (kind == "supersmoother") or (kind == "boxcar"):
# Interpolate back onto the original time array
interp_func = interpolate.interp1d(x_vals, y_fit)
if which.lower() == "phased":
# try:
smoothed_flux = interp_func(phased_time)
# except ValueError:
# # print(min(x_vals),max(x_vals))
# # print(min(phased_time),max(phased_time))
# smoothed_flux = np.ones_like(phased_time)
# smoothed_flux[1:-1] = interp_func(phased_time[1:-1])
# smoothed_flux[0] = smoothed_flux[1]
# smoothed_flux[-1] = smoothed_flux[-2]
elif which.lower() == "full":
smoothed_flux = interp_func(time)
else:
logging.warning("unknown which %s !!!", which)
# Whiten the input flux by subtracting the smoothed version
# The smoothed flux represents the "bulk trend"
white_flux = flux - smoothed_flux
white_unc = unc_flux
return white_flux, white_unc, smoothed_flux
def predict(self, t, filts=None, period=None):
"""Predict the supersmoother model for the data"""
if period is None:
raise ValueError("Must provide a period for the prediction")
model = ssm.SuperSmoother().fit(self.t % period, self.y, self.dy)
return model.predict(t % period)
