get_jitter.py

#from github.com/gdetor/SPySort

def get_jitter(self, evts, center, centerD, centerDD):
    """ Estimates the jitter given an event or a matrix of events where
    individual events form the rows, a median event and the first two
    derivatives of the latter.

    **Parameters**

    evts : double (array)
        The actual clean events to be realigned

    center : double (array)
        The estimate of the center (obtained from the median)

    centerD : double (array)
        The estimate of the center's derivative (obtained from the median
        of events cut on the derivative of data)

    centerDD : double (array)
        The estimate of the center's second derivative (obtained from the
        median of events cut on the second derivative of data)

    **Returns**

    The first approximation of the jitter (numerical value).
    """
    centerD_norm2 = np.dot(centerD, centerD)
    centerDD_norm2 = np.dot(centerDD, centerDD)
    centerD_dot_centerDD = np.dot(centerD, centerDD)

    if evts.ndim == 1:
        evts = evts.reshape(1, len(center))

    evts = evts - center
    h_dot_centerD = np.dot(evts, centerD)
    delta0 = h_dot_centerD/centerD_norm2
    h_dot_centerDD = np.dot(evts, centerDD)
    first = (-2. * h_dot_centerD + 2. * delta0 *
             (centerD_norm2 - h_dot_centerDD) + 3. * delta0**2 *
             centerD_dot_centerDD + delta0**3 * centerDD_norm2)
    second = (2. * (centerD_norm2 - h_dot_centerDD) + 6. * delta0 *
              centerD_dot_centerDD + 3. * delta0**2 * centerDD_norm2)
    return delta0 - first/second