DOC on attribute-parameter correspondence
@@ -89,6 +89,13 @@ General Concepts
:term:`feature_importances_`.
Common attributes are listed :ref:`below <glossary_attributes>`.
+ A public attribute may have the same name as a constructor
+ :term:`parameter`, with a ``_`` appended. This is used to store a
+ validated or estimated version of the user's input. For example,
+ :class:`decomposition.PCA` is constructed with an ``n_components``
+ parameter. From this, together with other parameters and the data,
+ PCA estimates the attribute ``n_components_``.
+
Further private attributes used in prediction/transformation/etc. may
also be set when fitting. These begin with a single underscore and are
not assured to be stable for public access.
