swm.py 文件源码

def _compute_J(x, window_starts, L):
    """Compute the cost, which is proportional to the
    difference between pairs of windows"""

    # Get all windows and zscore them
    N_windows = len(window_starts)
    windows = np.zeros((N_windows, L))
    for w in range(N_windows):
        temp = x[window_starts[w]:window_starts[w] + L]
        windows[w] = (temp - np.mean(temp)) / np.std(temp)

    # Calculate distances for all pairs of windows
    dist = pdist(np.vstack(windows),
                 lambda u, v: np.sum((u - v) ** 2))
    J = np.sum(dist) / float(L * (N_windows - 1))

    return J