def test_precision(self):
itp_x2 = WaryInterpolator(points=(0, 1, 2), values=(0, 1, 4), precision=0.01, domain=(0, 5))
self.assertRaises(InsufficientPrecisionError, itp_x2, 0.5)
xs = np.array([0.485, 0.495, 0.505, 0.515])
itp_x2.add_points(xs, xs**2)
self.assertAlmostEqual(itp_x2(0.5), (0.495**2 + 0.505**2)/2)
def test_interpolate(self):
itp = WaryInterpolator(if_higher='extrapolate', if_lower='raise', domain=(0, 5))
self.assertRaises(InsufficientPrecisionError, itp, 0)
itp.add_points([0, 2, 4], [10, 20, 30])
self.assertEqual(itp(0), 10)
self.assertAlmostEqual(itp(1), 15)
self.assertAlmostEqual(itp(5), 35)
self.assertRaises(OutsideDomainError, itp, -5)
def test_add_points(self):
itp1 = WaryInterpolator(domain=[0, 5])
itp1.add_points([0, 4, 2], [10, 30, 20])
itp2 = WaryInterpolator(points=(0, 2, 4), values=(10, 20, 30), domain=[0, 5])
np.testing.assert_array_equal(itp1.points, itp2.points)
np.testing.assert_array_equal(itp1.values, itp2.values)
itp1.add_point(4, 40)
itp2.add_point(4, 40)
np.testing.assert_array_equal(itp1.points, itp2.points)
np.testing.assert_array_equal(itp1.values, itp2.values)
def __init__(self, statistic, **kwargs):
self.statistic = statistic
for k, v in kwargs.items():
setattr(self, k, v)
self.cl = self.confidence_level
self.log = logging.getLogger(self.__class__.__name__)
if self.wrap_interpolator:
self.log.debug("Initializing interpolators")
if self.fixed_lower_limit is None:
self.low_limit_interpolator = WaryInterpolator(precision=10**(-self.precision_digits),
domain=self.interpolator_log_domain)
if self.fixed_upper_limit is None:
self.high_limit_interpolator = WaryInterpolator(precision=10**(-self.precision_digits),
domain=self.interpolator_log_domain)
# "Joints" of the interpolator must have better precision than required of the interpolator results
self.precision_digits += 1
# Dictionary holding "horizontal" intervals: interval on statistic for each precision and hypothesis.
self.cached_intervals = {}
class IntervalChoice(object):
"""Base interval choice method class
"""
method = 'rank' # 'rank' or 'threshold'
threshold = float('inf')
precision_digits = 2
use_interval_cache = True
wrap_interpolator = True
background = 0
confidence_level = 0.9
max_hypothesis = 1e6
interpolator_log_domain = (-1, 3)
fixed_upper_limit = None
fixed_lower_limit = None
# Use only for testing:
forbid_exact_computation = False
def __init__(self, statistic, **kwargs):
self.statistic = statistic
for k, v in kwargs.items():
setattr(self, k, v)
self.cl = self.confidence_level
self.log = logging.getLogger(self.__class__.__name__)
if self.wrap_interpolator:
self.log.debug("Initializing interpolators")
if self.fixed_lower_limit is None:
self.low_limit_interpolator = WaryInterpolator(precision=10**(-self.precision_digits),
domain=self.interpolator_log_domain)
if self.fixed_upper_limit is None:
self.high_limit_interpolator = WaryInterpolator(precision=10**(-self.precision_digits),
domain=self.interpolator_log_domain)
# "Joints" of the interpolator must have better precision than required of the interpolator results
self.precision_digits += 1
# Dictionary holding "horizontal" intervals: interval on statistic for each precision and hypothesis.
self.cached_intervals = {}
def get_interval_on_statistic(self, hypothesis, precision_digits):
"""Returns the self.cl confidence level interval on self.statistic for the event rate hypothesis
The event rate here includes signal as well as identically distributed background.
Intervals are inclusive = closed.
"""
if self.use_interval_cache and (hypothesis, precision_digits) in self.cached_intervals:
return self.cached_intervals[(hypothesis, precision_digits)]
stat_values, likelihoods = self.statistic.get_values_and_likelihoods(hypothesis,
precision_digits=precision_digits)
likelihoods = likelihoods / np.sum(likelihoods)
# Score each statistic value (method-dependent)
stat_value_scores = self.score_stat_values(statistic_values=stat_values,
likelihoods=likelihoods,
hypothesis=hypothesis)
if self.method == 'threshold':
# Include all statistic values that score higher than some threshold
values_in_interval = stat_values[stat_value_scores > self.get_threshold()]
else:
# Include the values with highest score first, until we reach the desired confidence level
# TODO: wouldn't HIGHEST score first be more user-friendly?
ranks = np.argsort(stat_value_scores)
train_values_sorted = stat_values[ranks]
likelihoods_sorted = likelihoods[ranks]
# Find the last value to include
# (= first value that takes the included probability over the required confidence level)
sum_lhoods = np.cumsum(likelihoods_sorted)
last_index = np.where(sum_lhoods > self.cl)[0][0] # TODO: can fail?
values_in_interval = train_values_sorted[:last_index + 1]
# Limits = extreme values in the interval.
# This means we will be conservative if values_in_interval is not continuous.
low_lim, high_lim = values_in_interval.min(), values_in_interval.max()
# If we included all values given up until a boundary, don't set that boundary as a limit
if low_lim == np.min(stat_values):
low_lim = 0
if high_lim == np.max(stat_values):
high_lim = float('inf')
# Cache and return upper and lower limit on the statistic
if self.use_interval_cache:
self.cached_intervals[(hypothesis, precision_digits)] = low_lim, high_lim
return low_lim, high_lim
def get_confidence_interval(self, value, precision_digits, search_region, debug=False):
"""Performs the Neynman construction to get confidence interval on event rate (mu),
if the statistic is observed to have value
"""
log_value = np.log10(value)
if self.wrap_interpolator:
# Try to interpolate the limit from limits computed earlier
self.log.debug("Trying to get values from interpolators")
try:
if self.fixed_lower_limit is None:
low_limit = 10**(self.low_limit_interpolator(log_value))
else:
low_limit = self.fixed_lower_limit
if self.fixed_upper_limit is None:
high_limit = 10**(self.high_limit_interpolator(log_value))
else:
high_limit = self.fixed_upper_limit
return low_limit, high_limit
except InsufficientPrecisionError:
self.log.debug("Insuffienct precision achieved by interpolators")
if log_value > self.interpolator_log_domain[1]:
self.log.debug("Too high value to dare to start Neyman construction... raising exception")
# It is not safe to do the Neyman construction: too high statistics
raise
self.log.debug("Log value %s is below interpolator log domain max %s "
"=> starting Neyman construction" % (log_value, self.interpolator_log_domain[1]))
except OutsideDomainError:
# The value is below the interpolator domain (e.g. 0 while the domain ends at 10**0 = 1)
pass
if self.forbid_exact_computation:
raise RuntimeError("Exact computation triggered")
def is_value_in(mu):
low_lim, high_lim = self.get_interval_on_statistic(mu + self.background,
precision_digits=precision_digits)
return low_lim <= value <= high_lim
# We first need one value in the interval to bound the limit searches
try:
true_point, low_search_bound, high_search_bound = search_true_instance(is_value_in,
*search_region,
precision_digits=precision_digits)
except SearchFailedException as e:
self.log.debug("Exploratory search could not find a single value in the interval! "
"This is probably a problem with search region, or simply a very extreme case."
"Original exception: %s" % str(e))
if is_value_in(0):
self.log.debug("Oh, ok, only zero is in the interval... Returning (0, 0)")
return 0, 0
return 0, float('inf')
self.log.debug(">>> Exploratory search completed: %s is in interval, "
"search for boundaries in [%s, %s]" % (true_point, low_search_bound, high_search_bound))
if self.fixed_lower_limit is not None:
low_limit = self.fixed_lower_limit
elif is_value_in(low_search_bound):
# If mu=0 can't be excluded, we're apparently only setting an upper limit (mu <= ..)
low_limit = 0
else:
low_limit = bisect_search(is_value_in, low_search_bound, true_point, precision_digits=precision_digits)
self.log.debug(">>> Low limit found at %s" % low_limit)
if self.fixed_upper_limit is not None:
low_limit = self.fixed_upper_limit
elif is_value_in(high_search_bound):
# If max_mu can't be excluded, we're apparently only setting a lower limit (mu >= ..)
high_limit = float('inf')
else:
high_limit = bisect_search(is_value_in, true_point, high_search_bound, precision_digits=precision_digits)
self.log.debug(">>> High limit found at %s" % high_limit)
if self.wrap_interpolator:
# Add the values to the interpolator, if they are within the domain
# TODO: Think about dealing with inf
if self.interpolator_log_domain[0] <= log_value <= self.interpolator_log_domain[1]:
if self.fixed_lower_limit is None:
self.low_limit_interpolator.add_point(log_value, np.log10(low_limit))
if self.fixed_upper_limit is None:
self.high_limit_interpolator.add_point(log_value, np.log10(high_limit))
return low_limit, high_limit
def score_stat_values(self, **kwargs):
# Return "rank" of each hypothesis. Hypotheses with highest ranks will be included first.
raise NotImplementedError()
def __call__(self, observation, precision_digits=None, search_region=None):
"""Perform Neynman construction to get confidence interval on event rate for observation.
"""
if precision_digits is None:
precision_digits = self.precision_digits
if search_region is None:
search_region = [0, round_to_digits(10 + 3 * len(observation), precision_digits)]
if self.statistic.mu_dependent:
value = self.statistic(observation, self.statistic.mus)
else:
value = self.statistic(observation, None)
self.log.debug("Statistic evaluates to %s" % value)
return self.get_confidence_interval(value, precision_digits=precision_digits, search_region=search_region)
