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# Source code for astropy.timeseries.periodograms.bls.core

    # Licensed under a 3-clause BSD style license - see LICENSE.rst

    __all__ = ["BoxLeastSquares", "BoxLeastSquaresResults"]

    import numpy as np

    from astropy import units
    from astropy import units as u
    from astropy.time import Time, TimeDelta
    from astropy.timeseries.periodograms.base import BasePeriodogram
    from astropy.timeseries.periodograms.lombscargle.core import has_units, strip_units

    from . import methods

    def validate_unit_consistency(reference_object, input_object):
        if has_units(reference_object):
            input_object = units.Quantity(input_object, unit=reference_object.unit)
        else:
            if has_units(input_object):
                input_object = units.Quantity(input_object, unit=units.one)
                input_object = input_object.value
        return input_object

    class BoxLeastSquares(BasePeriodogram):
        """Compute the box least squares periodogram

        This method is a commonly used tool for discovering transiting exoplanets
        or eclipsing binaries in photometric time series datasets. This
        implementation is based on the "box least squares (BLS)" method described
        in [1]_ and [2]_.

        Parameters
        ----------
        t : array-like, `~astropy.units.Quantity`, `~astropy.time.Time`, or `~astropy.time.TimeDelta`
            Sequence of observation times.
        y : array-like or `~astropy.units.Quantity`
            Sequence of observations associated with times ``t``.
        dy : float, array-like, or `~astropy.units.Quantity`, optional
            Error or sequence of observational errors associated with times ``t``.

        Examples
        --------
        Generate noisy data with a transit:

        >>> rand = np.random.default_rng(42)
        >>> t = rand.uniform(0, 10, 500)
        >>> y = np.ones_like(t)
        >>> y[np.abs((t + 1.0)%2.0-1)<0.08] = 1.0 - 0.1
        >>> y += 0.01 * rand.standard_normal(len(t))

        Compute the transit periodogram on a heuristically determined period grid
        and find the period with maximum power:

        >>> model = BoxLeastSquares(t, y)
        >>> results = model.autopower(0.16)
        >>> results.period[np.argmax(results.power)]  # doctest: +FLOAT_CMP
        2.000412388152837

        Compute the periodogram on a user-specified period grid:

        >>> periods = np.linspace(1.9, 2.1, 5)
        >>> results = model.power(periods, 0.16)
        >>> results.power  # doctest: +FLOAT_CMP
        array([0.01723948, 0.0643028 , 0.1338783 , 0.09428816, 0.03577543])

        If the inputs are AstroPy Quantities with units, the units will be
        validated and the outputs will also be Quantities with appropriate units:

        >>> from astropy import units as u
        >>> t = t * u.day
        >>> y = y * u.dimensionless_unscaled
        >>> model = BoxLeastSquares(t, y)
        >>> results = model.autopower(0.16 * u.day)
        >>> results.period.unit
        Unit("d")
        >>> results.power.unit
        Unit(dimensionless)

        References
        ----------
        .. [1] Kovacs, Zucker, & Mazeh (2002), A&A, 391, 369
            (arXiv:astro-ph/0206099)
        .. [2] Hartman & Bakos (2016), Astronomy & Computing, 17, 1
            (arXiv:1605.06811)

        """

        def __init__(self, t, y, dy=None):
            # If t is a TimeDelta, convert it to a quantity. The units we convert
            # to don't really matter since the user gets a Quantity back at the end
            # so can convert to any units they like.
            if isinstance(t, TimeDelta):
                t = t.to("day")

            # We want to expose self.t as being the times the user passed in, but
            # if the times are absolute, we need to convert them to relative times
            # internally, so we use self._trel and self._tstart for this.

            self.t = t

            if isinstance(self.t, (Time, TimeDelta)):
                self._tstart = self.t[0]
                trel = (self.t - self._tstart).to(u.day)
            else:
                self._tstart = None
                trel = self.t

            self._trel, self.y, self.dy = self._validate_inputs(trel, y, dy)

        def autoperiod(
            self,
            duration,
            minimum_period=None,
            maximum_period=None,
            minimum_n_transit=3,
            frequency_factor=1.0,
        ):
            """Determine a suitable grid of periods

            This method uses a set of heuristics to select a conservative period
            grid that is uniform in frequency. This grid might be too fine for
            some user's needs depending on the precision requirements or the
            sampling of the data. The grid can be made coarser by increasing
            ``frequency_factor``.

            Parameters
            ----------
            duration : float, array-like, or `~astropy.units.Quantity` ['time']
                The set of durations that will be considered.
            minimum_period, maximum_period : float or `~astropy.units.Quantity` ['time'], optional
                The minimum/maximum periods to search. If not provided, these will
                be computed as described in the notes below.
            minimum_n_transit : int, optional
                If ``maximum_period`` is not provided, this is used to compute the
                maximum period to search by asserting that any systems with at
                least ``minimum_n_transits`` will be within the range of searched
                periods. Note that this is not the same as requiring that
                ``minimum_n_transits`` be required for detection. The default
                value is ``3``.
            frequency_factor : float, optional
                A factor to control the frequency spacing as described in the
                notes below. The default value is ``1.0``.

            Returns
            -------
            period : array-like or `~astropy.units.Quantity` ['time']
                The set of periods computed using these heuristics with the same
                units as ``t``.

            Notes
            -----
            The default minimum period is chosen to be twice the maximum duration
            because there won't be much sensitivity to periods shorter than that.

            The default maximum period is computed as

            .. code-block:: python

                maximum_period = (max(t) - min(t)) / minimum_n_transits

            ensuring that any systems with at least ``minimum_n_transits`` are
            within the range of searched periods.

            The frequency spacing is given by

            .. code-block:: python

                df = frequency_factor * min(duration) / (max(t) - min(t))**2

            so the grid can be made finer by decreasing ``frequency_factor`` or
            coarser by increasing ``frequency_factor``.

            """

            duration = self._validate_duration(duration)
            baseline = strip_units(self._trel.max() - self._trel.min())
            min_duration = strip_units(np.min(duration))

            # Estimate the required frequency spacing
            # Because of the sparsity of a transit, this must be much finer than
            # the frequency resolution for a sinusoidal fit. For a sinusoidal fit,
            # df would be 1/baseline (see LombScargle), but here this should be
            # scaled proportionally to the duration in units of baseline.
            df = frequency_factor * min_duration / baseline**2

            # If a minimum period is not provided, choose one that is twice the
            # maximum duration because we won't be sensitive to any periods
            # shorter than that.
            if minimum_period is None:
                minimum_period = 2.0 * strip_units(np.max(duration))
            else:
                minimum_period = validate_unit_consistency(self._trel, minimum_period)
                minimum_period = strip_units(minimum_period)

            # If no maximum period is provided, choose one by requiring that
            # all signals with at least minimum_n_transit should be detectable.
            if maximum_period is None:
                if minimum_n_transit <= 1:
                    raise ValueError("minimum_n_transit must be greater than 1")
                maximum_period = baseline / (minimum_n_transit - 1)
            else:
                maximum_period = validate_unit_consistency(self._trel, maximum_period)
                maximum_period = strip_units(maximum_period)

            if maximum_period < minimum_period:
                minimum_period, maximum_period = maximum_period, minimum_period
            if minimum_period <= 0.0:
                raise ValueError("minimum_period must be positive")

            # Convert bounds to frequency
            minimum_frequency = 1.0 / strip_units(maximum_period)
            maximum_frequency = 1.0 / strip_units(minimum_period)

            # Compute the number of frequencies and the frequency grid
            nf = 1 + int(np.round((maximum_frequency - minimum_frequency) / df))
            return 1.0 / (maximum_frequency - df * np.arange(nf)) * self._t_unit()

        def autopower(
            self,
            duration,
            objective=None,
            method=None,
            oversample=10,
            minimum_n_transit=3,
            minimum_period=None,
            maximum_period=None,
            frequency_factor=1.0,
        ):
            """Compute the periodogram at set of heuristically determined periods

            This method calls :func:`BoxLeastSquares.autoperiod` to determine
            the period grid and then :func:`BoxLeastSquares.power` to compute
            the periodogram. See those methods for documentation of the arguments.

            """
            period = self.autoperiod(
                duration,
                minimum_n_transit=minimum_n_transit,
                minimum_period=minimum_period,
                maximum_period=maximum_period,
                frequency_factor=frequency_factor,
            )
            return self.power(
                period, duration, objective=objective, method=method, oversample=oversample
            )

        def power(self, period, duration, objective=None, method=None, oversample=10):
            """Compute the periodogram for a set of periods

            Parameters
            ----------
            period : array-like or `~astropy.units.Quantity` ['time']
                The periods where the power should be computed
            duration : float, array-like, or `~astropy.units.Quantity` ['time']
                The set of durations to test
            objective : {'likelihood', 'snr'}, optional
                The scalar that should be optimized to find the best fit phase,
                duration, and depth. This can be either ``'likelihood'`` (default)
                to optimize the log-likelihood of the model, or ``'snr'`` to
                optimize the signal-to-noise with which the transit depth is
                measured.
            method : {'fast', 'slow'}, optional
                The computational method used to compute the periodogram. This is
                mainly included for the purposes of testing and most users will
                want to use the optimized ``'fast'`` method (default) that is
                implemented in Cython.  ``'slow'`` is a brute-force method that is
                used to test the results of the ``'fast'`` method.
            oversample : int, optional
                The number of bins per duration that should be used. This sets the
                time resolution of the phase fit with larger values of
                ``oversample`` yielding a finer grid and higher computational cost.

            Returns
            -------
            results : BoxLeastSquaresResults
                The periodogram results as a :class:`BoxLeastSquaresResults`
                object.

            Raises
            ------
            ValueError
                If ``oversample`` is not an integer greater than 0 or if
                ``objective`` or ``method`` are not valid.

            """
            period, duration = self._validate_period_and_duration(period, duration)

            # Check for absurdities in the ``oversample`` choice
            try:
                oversample = int(oversample)
            except TypeError:
                raise ValueError(f"oversample must be an int, got {oversample}")
            if oversample < 1:
                raise ValueError("oversample must be greater than or equal to 1")

            # Select the periodogram objective
            if objective is None:
                objective = "likelihood"
            allowed_objectives = ["snr", "likelihood"]
            if objective not in allowed_objectives:
                raise ValueError(
                    f"Unrecognized method '{objective}'\n"
                    f"allowed methods are: {allowed_objectives}"
                )
            use_likelihood = objective == "likelihood"

            # Select the computational method
            if method is None:
                method = "fast"
            allowed_methods = ["fast", "slow"]
            if method not in allowed_methods:
                raise ValueError(
                    f"Unrecognized method '{method}'\n"
                    f"allowed methods are: {allowed_methods}"
                )

            # Format and check the input arrays
            t = np.ascontiguousarray(strip_units(self._trel), dtype=np.float64)
            t_ref = np.min(t)
            y = np.ascontiguousarray(strip_units(self.y), dtype=np.float64)
            if self.dy is None:
                ivar = np.ones_like(y)
            else:
                ivar = (
                    1.0 / np.ascontiguousarray(strip_units(self.dy), dtype=np.float64) ** 2
                )

            # Make sure that the period and duration arrays are C-order
            period_fmt = np.ascontiguousarray(strip_units(period), dtype=np.float64)
            duration = np.ascontiguousarray(strip_units(duration), dtype=np.float64)

            # Select the correct implementation for the chosen method
            if method == "fast":
                bls = methods.bls_fast
            else:
                bls = methods.bls_slow

            # Run the implementation
            results = bls(
                t - t_ref,
                y - np.median(y),
                ivar,
                period_fmt,
                duration,
                oversample,
                use_likelihood,
            )

            return self._format_results(t_ref, objective, period, results)

        def _as_relative_time(self, name, times):
            """
            Convert the provided times (if absolute) to relative times using the
            current _tstart value. If the times provided are relative, they are
            returned without conversion (though we still do some checks).
            """

            if isinstance(times, TimeDelta):
                times = times.to("day")

            if self._tstart is None:
                if isinstance(times, Time):
                    raise TypeError(
                        f"{name} was provided as an absolute time but "
                        "the BoxLeastSquares class was initialized "
                        "with relative times."
                    )
            else:
                if isinstance(times, Time):
                    times = (times - self._tstart).to(u.day)
                else:
                    raise TypeError(
                        f"{name} was provided as a relative time but "
                        "the BoxLeastSquares class was initialized "
                        "with absolute times."
                    )

            times = validate_unit_consistency(self._trel, times)

            return times

        def _as_absolute_time_if_needed(self, name, times):
            """
            Convert the provided times to absolute times using the current _tstart
            value, if needed.
            """
            if self._tstart is not None:
                # Some time formats/scales can't represent dates/times too far
                # off from the present, so we need to mask values offset by
                # more than 100,000 yr (the periodogram algorithm can return
                # transit times of e.g 1e300 for some periods).
                reset = np.abs(times.to_value(u.year)) > 100000
                times[reset] = 0
                times = self._tstart + times
                times[reset] = np.nan
            return times

        def model(self, t_model, period, duration, transit_time):
            """Compute the transit model at the given period, duration, and phase

            Parameters
            ----------
            t_model : array-like, `~astropy.units.Quantity`, or `~astropy.time.Time`
                Times at which to compute the model.
            period : float or `~astropy.units.Quantity` ['time']
                The period of the transits.
            duration : float or `~astropy.units.Quantity` ['time']
                The duration of the transit.
            transit_time : float or `~astropy.units.Quantity` or `~astropy.time.Time`
                The mid-transit time of a reference transit.

            Returns
            -------
            y_model : array-like or `~astropy.units.Quantity`
                The model evaluated at the times ``t_model`` with units of ``y``.

            """

            period, duration = self._validate_period_and_duration(period, duration)

            transit_time = self._as_relative_time("transit_time", transit_time)
            t_model = strip_units(self._as_relative_time("t_model", t_model))

            period = float(strip_units(period))
            duration = float(strip_units(duration))
            transit_time = float(strip_units(transit_time))

            t = np.ascontiguousarray(strip_units(self._trel), dtype=np.float64)
            y = np.ascontiguousarray(strip_units(self.y), dtype=np.float64)
            if self.dy is None:
                ivar = np.ones_like(y)
            else:
                ivar = (
                    1.0 / np.ascontiguousarray(strip_units(self.dy), dtype=np.float64) ** 2
                )

            # Compute the depth
            hp = 0.5 * period
            m_in = np.abs((t - transit_time + hp) % period - hp) < 0.5 * duration
            m_out = ~m_in
            y_in = np.sum(y[m_in] * ivar[m_in]) / np.sum(ivar[m_in])
            y_out = np.sum(y[m_out] * ivar[m_out]) / np.sum(ivar[m_out])

            # Evaluate the model
            y_model = y_out + np.zeros_like(t_model)
            m_model = np.abs((t_model - transit_time + hp) % period - hp) < 0.5 * duration
            y_model[m_model] = y_in

            return y_model * self._y_unit()

        def compute_stats(self, period, duration, transit_time):
            """Compute descriptive statistics for a given transit model

            These statistics are commonly used for vetting of transit candidates.

            Parameters
            ----------
            period : float or `~astropy.units.Quantity` ['time']
                The period of the transits.
            duration : float or `~astropy.units.Quantity` ['time']
                The duration of the transit.
            transit_time : float or `~astropy.units.Quantity` or `~astropy.time.Time`
                The mid-transit time of a reference transit.

            Returns
            -------
            stats : dict
                A dictionary containing several descriptive statistics:

                - ``depth``: The depth and uncertainty (as a tuple with two
                    values) on the depth for the fiducial model.
                - ``depth_odd``: The depth and uncertainty on the depth for a
                    model where the period is twice the fiducial period.
                - ``depth_even``: The depth and uncertainty on the depth for a
                    model where the period is twice the fiducial period and the
                    phase is offset by one orbital period.
                - ``depth_half``: The depth and uncertainty for a model with a
                    period of half the fiducial period.
                - ``depth_phased``: The depth and uncertainty for a model with the
                    fiducial period and the phase offset by half a period.
                - ``harmonic_amplitude``: The amplitude of the best fit sinusoidal
                    model.
                - ``harmonic_delta_log_likelihood``: The difference in log
                    likelihood between a sinusoidal model and the transit model.
                    If ``harmonic_delta_log_likelihood`` is greater than zero, the
                    sinusoidal model is preferred.
                - ``transit_times``: The mid-transit time for each transit in the
                    baseline.
                - ``per_transit_count``: An array with a count of the number of
                    data points in each unique transit included in the baseline.
                - ``per_transit_log_likelihood``: An array with the value of the
                    log likelihood for each unique transit included in the
                    baseline.

            """

            period, duration = self._validate_period_and_duration(period, duration)
            transit_time = self._as_relative_time("transit_time", transit_time)

            period = float(strip_units(period))
            duration = float(strip_units(duration))
            transit_time = float(strip_units(transit_time))

            t = np.ascontiguousarray(strip_units(self._trel), dtype=np.float64)
            y = np.ascontiguousarray(strip_units(self.y), dtype=np.float64)
            if self.dy is None:
                ivar = np.ones_like(y)
            else:
                ivar = (
                    1.0 / np.ascontiguousarray(strip_units(self.dy), dtype=np.float64) ** 2
                )

            # This a helper function that will compute the depth for several
            # different hypothesized transit models with different parameters
            def _compute_depth(m, y_out=None, var_out=None):
                if np.any(m) and (var_out is None or np.isfinite(var_out)):
                    var_m = 1.0 / np.sum(ivar[m])
                    y_m = np.sum(y[m] * ivar[m]) * var_m
                    if y_out is None:
                        return y_m, var_m
                    return y_out - y_m, np.sqrt(var_m + var_out)
                return 0.0, np.inf

            # Compute the depth of the fiducial model and the two models at twice
            # the period
            hp = 0.5 * period
            m_in = np.abs((t - transit_time + hp) % period - hp) < 0.5 * duration
            m_out = ~m_in
            m_odd = np.abs((t - transit_time) % (2 * period) - period) < 0.5 * duration
            m_even = (
                np.abs((t - transit_time + period) % (2 * period) - period) < 0.5 * duration
            )

            y_out, var_out = _compute_depth(m_out)
            depth = _compute_depth(m_in, y_out, var_out)
            depth_odd = _compute_depth(m_odd, y_out, var_out)
            depth_even = _compute_depth(m_even, y_out, var_out)
            y_in = y_out - depth[0]

            # Compute the depth of the model at a phase of 0.5*period
            m_phase = np.abs((t - transit_time) % period - hp) < 0.5 * duration
            depth_phase = _compute_depth(m_phase, *_compute_depth((~m_phase) & m_out))

            # Compute the depth of a model with a period of 0.5*period
            m_half = (
                np.abs((t - transit_time + 0.25 * period) % (0.5 * period) - 0.25 * period)
                < 0.5 * duration
            )
            depth_half = _compute_depth(m_half, *_compute_depth(~m_half))

            # Compute the number of points in each transit
            transit_id = np.round((t[m_in] - transit_time) / period).astype(int)
            transit_times = (
                period * np.arange(transit_id.min(), transit_id.max() + 1) + transit_time
            )
            unique_ids, unique_counts = np.unique(transit_id, return_counts=True)
            unique_ids -= np.min(transit_id)
            transit_id -= np.min(transit_id)
            counts = np.zeros(np.max(transit_id) + 1, dtype=int)
            counts[unique_ids] = unique_counts

            # Compute the per-transit log likelihood
            ll = -0.5 * ivar[m_in] * ((y[m_in] - y_in) ** 2 - (y[m_in] - y_out) ** 2)
            lls = np.zeros(len(counts))
            for i in unique_ids:
                lls[i] = np.sum(ll[transit_id == i])
            full_ll = -0.5 * np.sum(ivar[m_in] * (y[m_in] - y_in) ** 2)
            full_ll -= 0.5 * np.sum(ivar[m_out] * (y[m_out] - y_out) ** 2)

            # Compute the log likelihood of a sine model
            A = np.vstack(
                (
                    np.sin(2 * np.pi * t / period),
                    np.cos(2 * np.pi * t / period),
                    np.ones_like(t),
                )
            ).T
            w = np.linalg.solve(np.dot(A.T, A * ivar[:, None]), np.dot(A.T, y * ivar))
            mod = np.dot(A, w)
            sin_ll = -0.5 * np.sum((y - mod) ** 2 * ivar)

            # Format the results
            y_unit = self._y_unit()
            ll_unit = 1
            if self.dy is None:
                ll_unit = y_unit * y_unit
            return dict(
                transit_times=self._as_absolute_time_if_needed(
                    "transit_times", transit_times * self._t_unit()
                ),
                per_transit_count=counts,
                per_transit_log_likelihood=lls * ll_unit,
                depth=(depth[0] * y_unit, depth[1] * y_unit),
                depth_phased=(depth_phase[0] * y_unit, depth_phase[1] * y_unit),
                depth_half=(depth_half[0] * y_unit, depth_half[1] * y_unit),
                depth_odd=(depth_odd[0] * y_unit, depth_odd[1] * y_unit),
                depth_even=(depth_even[0] * y_unit, depth_even[1] * y_unit),
                harmonic_amplitude=np.sqrt(np.sum(w[:2] ** 2)) * y_unit,
                harmonic_delta_log_likelihood=(sin_ll - full_ll) * ll_unit,
            )

        def transit_mask(self, t, period, duration, transit_time):
            """Compute which data points are in transit for a given parameter set

            Parameters
            ----------
            t : array-like or `~astropy.units.Quantity` ['time']
                Times where the mask should be evaluated.
            period : float or `~astropy.units.Quantity` ['time']
                The period of the transits.
            duration : float or `~astropy.units.Quantity` ['time']
                The duration of the transit.
            transit_time : float or `~astropy.units.Quantity` or `~astropy.time.Time`
                The mid-transit time of a reference transit.

            Returns
            -------
            transit_mask : array-like
                A boolean array where ``True`` indicates and in transit point and
                ``False`` indicates and out-of-transit point.

            """

            period, duration = self._validate_period_and_duration(period, duration)
            transit_time = self._as_relative_time("transit_time", transit_time)
            t = strip_units(self._as_relative_time("t", t))

            period = float(strip_units(period))
            duration = float(strip_units(duration))
            transit_time = float(strip_units(transit_time))

            hp = 0.5 * period
            return np.abs((t - transit_time + hp) % period - hp) < 0.5 * duration

        def _validate_inputs(self, t, y, dy):
            """Private method used to check the consistency of the inputs

            Parameters
            ----------
            t : array-like, `~astropy.units.Quantity`, `~astropy.time.Time`, or `~astropy.time.TimeDelta`
                Sequence of observation times.
            y : array-like or `~astropy.units.Quantity`
                Sequence of observations associated with times t.
            dy : float, array-like, or `~astropy.units.Quantity`
                Error or sequence of observational errors associated with times t.

            Returns
            -------
            t, y, dy : array-like, `~astropy.units.Quantity`, or `~astropy.time.Time`
                The inputs with consistent shapes and units.

            Raises
            ------
            ValueError
                If the dimensions are incompatible or if the units of dy cannot be
                converted to the units of y.

            """

            # Validate shapes of inputs
            if dy is None:
                t, y = np.broadcast_arrays(t, y, subok=True)
            else:
                t, y, dy = np.broadcast_arrays(t, y, dy, subok=True)
            if t.ndim != 1:
                raise ValueError("Inputs (t, y, dy) must be 1-dimensional")

            # validate units of inputs if any is a Quantity
            if dy is not None:
                dy = validate_unit_consistency(y, dy)

            return t, y, dy

        def _validate_duration(self, duration):
            """Private method used to check a set of test durations

            Parameters
            ----------
            duration : float, array-like, or `~astropy.units.Quantity`
                The set of durations that will be considered.

            Returns
            -------
            duration : array-like or `~astropy.units.Quantity`
                The input reformatted with the correct shape and units.

            Raises
            ------
            ValueError
                If the units of duration cannot be converted to the units of t.

            """
            duration = np.atleast_1d(np.abs(duration))
            if duration.ndim != 1 or duration.size == 0:
                raise ValueError("duration must be 1-dimensional")
            return validate_unit_consistency(self._trel, duration)

        def _validate_period_and_duration(self, period, duration):
            """Private method used to check a set of periods and durations

            Parameters
            ----------
            period : float, array-like, or `~astropy.units.Quantity` ['time']
                The set of test periods.
            duration : float, array-like, or `~astropy.units.Quantity` ['time']
                The set of durations that will be considered.

            Returns
            -------
            period, duration : array-like or `~astropy.units.Quantity` ['time']
                The inputs reformatted with the correct shapes and units.

            Raises
            ------
            ValueError
                If the units of period or duration cannot be converted to the
                units of t.

            """
            duration = self._validate_duration(duration)
            period = np.atleast_1d(np.abs(period))
            if period.ndim != 1 or period.size == 0:
                raise ValueError("period must be 1-dimensional")
            period = validate_unit_consistency(self._trel, period)

            if not np.min(period) > np.max(duration):
                raise ValueError(
                    "The maximum transit duration must be shorter than the minimum period"
                )

            return period, duration

        def _format_results(self, t_ref, objective, period, results):
            """A private method used to wrap and add units to the periodogram

            Parameters
            ----------
            t_ref : float
                The minimum time in the time series (a reference time).
            objective : str
                The name of the objective used in the optimization.
            period : array-like or `~astropy.units.Quantity` ['time']
                The set of trial periods.
            results : tuple
                The output of one of the periodogram implementations.

            """
            (
                power,
                depth,
                depth_err,
                duration,
                transit_time,
                depth_snr,
                log_likelihood,
            ) = results
            transit_time += t_ref

            if has_units(self._trel):
                transit_time = units.Quantity(transit_time, unit=self._trel.unit)
                transit_time = self._as_absolute_time_if_needed(
                    "transit_time", transit_time
                )
                duration = units.Quantity(duration, unit=self._trel.unit)

            if has_units(self.y):
                depth = units.Quantity(depth, unit=self.y.unit)
                depth_err = units.Quantity(depth_err, unit=self.y.unit)

                depth_snr = units.Quantity(depth_snr, unit=units.one)

                if self.dy is None:
                    if objective == "likelihood":
                        power = units.Quantity(power, unit=self.y.unit**2)
                    else:
                        power = units.Quantity(power, unit=units.one)
                    log_likelihood = units.Quantity(log_likelihood, unit=self.y.unit**2)
                else:
                    power = units.Quantity(power, unit=units.one)
                    log_likelihood = units.Quantity(log_likelihood, unit=units.one)

            return BoxLeastSquaresResults(
                objective,
                period,
                power,
                depth,
                depth_err,
                duration,
                transit_time,
                depth_snr,
                log_likelihood,
            )

        def _t_unit(self):
            if has_units(self._trel):
                return self._trel.unit
            else:
                return 1

        def _y_unit(self):
            if has_units(self.y):
                return self.y.unit
            else:
                return 1

    class BoxLeastSquaresResults(dict):
        """The results of a BoxLeastSquares search

        Attributes
        ----------
        objective : str
            The scalar used to optimize to find the best fit phase, duration, and
            depth. See :func:`BoxLeastSquares.power` for more information.
        period : array-like or `~astropy.units.Quantity` ['time']
            The set of test periods.
        power : array-like or `~astropy.units.Quantity`
            The periodogram evaluated at the periods in ``period``. If
            ``objective`` is:

            * ``'likelihood'``: the values of ``power`` are the
              log likelihood maximized over phase, depth, and duration, or
            * ``'snr'``: the values of ``power`` are the signal-to-noise with
              which the depth is measured maximized over phase, depth, and
              duration.

        depth : array-like or `~astropy.units.Quantity`
            The estimated depth of the maximum power model at each period.
        depth_err : array-like or `~astropy.units.Quantity`
            The 1-sigma uncertainty on ``depth``.
        duration : array-like or `~astropy.units.Quantity` ['time']
            The maximum power duration at each period.
        transit_time : array-like, `~astropy.units.Quantity`, or `~astropy.time.Time`
            The maximum power phase of the transit in units of time. This
            indicates the mid-transit time and it will always be in the range
            (0, period).
        depth_snr : array-like or `~astropy.units.Quantity`
            The signal-to-noise with which the depth is measured at maximum power.
        log_likelihood : array-like or `~astropy.units.Quantity`
            The log likelihood of the maximum power model.

        """

        def __init__(self, *args):
            super().__init__(
                zip(
                    (
                        "objective",
                        "period",
                        "power",
                        "depth",
                        "depth_err",
                        "duration",
                        "transit_time",
                        "depth_snr",
                        "log_likelihood",
                    ),
                    args,
                )
            )

        def __getattr__(self, name):
            try:
                return self[name]
            except KeyError:
                raise AttributeError(name)

        __setattr__ = dict.__setitem__
        __delattr__ = dict.__delitem__

        def __repr__(self):
            if self.keys():
                m = max(map(len, list(self.keys()))) + 1
                return "\n".join(
                    [k.rjust(m) + ": " + repr(v) for k, v in sorted(self.items())]
                )
            else:
                return self.__class__.__name__ + "()"

        def __dir__(self):
            return list(self.keys())