def keepsaccade(i, j, sim_lenx, sim_leny, sim_x, sim_y, sim_theta, sim_len,
    sim_dur, data):
    """
    Helper function for scanpath simplification. If no simplification can be
    performed on a particular saccade, this functions stores the original data.
    :param i: current index
    :param j: current index
    :param sim_lenx: list
    :param sim_leny: list
    :param sim_x: list
    :param sim_y: list
    :param sim_theta: list
    :param sim_len: list
    :param sim_dur: list
    :param data: eyedata, list of list
    """
    sim_lenx.insert(j, data['saccade_lenx'][i])
    sim_leny.insert(j, data['saccade_leny'][i])
    sim_x.insert(j, data['saccade_x'][i])
    sim_y.insert(j, data['saccade_y'][i])
    sim_theta.insert(j, data['saccade_theta'][i])
    sim_len.insert(j, data['saccade_rho'][i])
    sim_dur.insert(j, data['fixation_dur'][i])
    i += 1
    j += 1
    return sim_lenx, sim_leny, sim_x, sim_y, sim_theta, sim_len, sim_dur, i, j
