DOC: improve docstring of AgglomerativeClustering
@@ -685,7 +685,8 @@ class AgglomerativeClustering(BaseEstimator, ClusterMixin):
Parameters
----------
X : array-like, shape = [n_samples, n_features]
- The samples a.k.a. observations.
+ Training data. Shape [n_samples, n_features], or [n_samples,
+ n_samples] if affinity=='precomputed'.
y : Ignored
