'Return negative loglikelihood function.
Notes
This is ``-sum(log pdf(x, theta), axis=0)`` where `theta` are the
parameters (including loc and scale).'

def nnlf(self, theta, x):

    (loc, scale, args) = self._unpack_loc_scale(theta)
    if ((not self._argcheck(*args)) or (scale <= 0)):
        return inf
    x = asarray(((x - loc) / scale))
    n_log_scale = (len(x) * log(scale))
    if np.any((~ self._support_mask(x))):
        return inf
    return (self._nnlf(x, *args) + n_log_scale)
