'clips out all data points that are more than a certain number
of standard deviations from the mean.
sigs can be either a single value or a length-p sequence that
specifies the number of standard deviations along each of the
p dimensions.'

def sigclip(self, sigs):

    if np.isscalar(sigs):
        sigs = (sigs * np.ones(self.N.shape[1]))
    sigs = (sigs * np.std(self.N, axis=1))
    n = self.N.shape[0]
    m = np.all((np.abs(self.N) < sigs), axis=1)
    self.A = self.A[m]
    self.__calc()
    return (n - sum(m))
