Calculates annualized alpha.

    Parameters
    ----------
    returns : pd.Series
        Daily returns of the strategy, noncumulative.
        - See full explanation in :func:`~empyrical.stats.cum_returns`.
    factor_returns : pd.Series
        Daily noncumulative returns of the factor to which beta is
        computed. Usually a benchmark such as the market.
        - This is in the same style as returns.
    risk_free : int, float, optional
        Constant risk-free return throughout the period. For example, the
        interest rate on a three month us treasury bill.
    period : str, optional
        Defines the periodicity of the 'returns' data for purposes of
        annualizing. Value ignored if `annualization` parameter is specified.
        Defaults are::

            'monthly':12
            'weekly': 52
            'daily': 252

    annualization : int, optional
        Used to suppress default values available in `period` to convert
        returns into annual returns. Value should be the annual frequency of
        `returns`.
        - See full explanation in :func:`~empyrical.stats.annual_return`.
    _beta : float, optional
        The beta for the given inputs, if already known. Will be calculated
        internally if not provided.
    out : array-like, optional
        Array to use as output buffer.
        If not passed, a new array will be created.

    Returns
    -------
    float
        Alpha.

def alpha(returns,
          factor_returns,
          risk_free=0.0,
          period=DAILY,
          annualization=None,
          out=None,
          _beta=None):
    """Calculates annualized alpha.

    Parameters
    ----------
    returns : pd.Series
        Daily returns of the strategy, noncumulative.
        - See full explanation in :func:`~empyrical.stats.cum_returns`.
    factor_returns : pd.Series
        Daily noncumulative returns of the factor to which beta is
        computed. Usually a benchmark such as the market.
        - This is in the same style as returns.
    risk_free : int, float, optional
        Constant risk-free return throughout the period. For example, the
        interest rate on a three month us treasury bill.
    period : str, optional
        Defines the periodicity of the 'returns' data for purposes of
        annualizing. Value ignored if `annualization` parameter is specified.
        Defaults are::

            'monthly':12
            'weekly': 52
            'daily': 252

    annualization : int, optional
        Used to suppress default values available in `period` to convert
        returns into annual returns. Value should be the annual frequency of
        `returns`.
        - See full explanation in :func:`~empyrical.stats.annual_return`.
    _beta : float, optional
        The beta for the given inputs, if already known. Will be calculated
        internally if not provided.
    out : array-like, optional
        Array to use as output buffer.
        If not passed, a new array will be created.

    Returns
    -------
    float
        Alpha.
    """
    if not (isinstance(returns, np.ndarray) and
            isinstance(factor_returns, np.ndarray)):
        returns, factor_returns = _aligned_series(returns, factor_returns)

    return alpha_aligned(
        returns,
        factor_returns,
        risk_free=risk_free,
        period=period,
        annualization=annualization,
        out=out,
        _beta=_beta
    )