为什么会收到群集警告？

Question

我试图在距离矩阵上执行层次聚集聚类。为此，我制作了一个kneighbors图，然后将其输入sklearn的聚集聚类算法。当我这样做的时候，它工作了，但是我得到了以下错误：

Warning (from warnings module):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/sklearn/cluster/hierarchical.py", line 463
    out = hierarchy.linkage(X, method=linkage, metric=affinity)
ClusterWarning: scipy.cluster: The symmetric non-negative hollow observation matrix looks suspiciously like an uncondensed distance matrix

我试过在其他地方寻找，但我似乎不明白为什么会抛出这个错误，如果它的工作和显示的数据。为什么会这样？（以下代码仅供参考）

plt.figure(figsize=(10, 6))
for index, linkage in enumerate(('average',
                                             'complete',
                                             'ward',
                                             'single')):
        plt.subplot(1, 4, index + 1)
        model = AgglomerativeClustering(linkage=linkage,
                                                connectivity=connectivity,
                                                n_clusters=n_clusters)
         t0 = time.time()
         model.fit(X)
                elapsed_time = time.time() - t0
         plt.scatter(X[:, 0], X[:, 1], c=model.labels_,
                            cmap=plt.cm.nipy_spectral)
         plt.title('linkage=%s\n(time %.2fs)' % (linkage, elapsed_time),
                          fontdict=dict(verticalalignment='top'))
         plt.axis('equal')
         plt.axis('off')

         plt.subplots_adjust(bottom=0, top=.89, wspace=0,
                                    left=0, right=1)
         plt.suptitle('n_cluster=%i, connectivity=%r' %
                             (n_clusters, connectivity is not None), size=17)
plt.show()