def alpha(algorithm_returns, treasury_return, benchmark_returns, beta):
    """
    http://en.wikipedia.org/wiki/Alpha_(investment)
    Args:
        algorithm_period_return (float):
            Return percentage from algorithm period.
        treasury_period_return (float):
            Return percentage for treasury period.
        benchmark_period_return (float):
            Return percentage for benchmark period.
        beta (float):
            beta value for the same period as all other values
    Returns:
        float. The alpha of the algorithm.
    """
    return algorithm_returns - (treasury_return + beta * (benchmark_returns -
        treasury_return))
