Calculate Chi from True Positive (tp), True Negative (tn), False Positive/Negative counts.
    Assumes that the random variable being measured is continuous rather than discrete.
    Reference:
      https://en.wikipedia.org/wiki/Matthews_correlation_coefficient
    >>> round(tptnfpfn_chi(1000, 2000, 30, 40))
    2765.0

def tptnfpfn_chi(*args, **kwargs):
    """Calculate Chi from True Positive (tp), True Negative (tn), False Positive/Negative counts.
    Assumes that the random variable being measured is continuous rather than discrete.
    Reference:
      https://en.wikipedia.org/wiki/Matthews_correlation_coefficient
    >>> round(tptnfpfn_chi(1000, 2000, 30, 40))
    2765.0
    """
    tp, tn, fp, fn = args_tptnfpfn(*args, **kwargs)
    return tptnfpfn_mcc(tp=tp, tn=tn, fp=fp, fn=fn) ** 2. * (tp + tn + fp + fn)