def unpack_trace(data):
    """
    Extract axes and data from a packed data matrix.

    Returns
    -------
    t     (M,) np.ndarray
    wl    (N,) np.ndarray
    trace (M, N) np.ndarray
    """
    wl = data[1:,0]
    t = data[0,1:]
    trace = data[1:,1:]
    return t, wl, trace