DOC glossary notes on warm_start
@@ -1547,9 +1547,15 @@ functions or non-estimator constructors.
their number.
:term:`partial_fit` also retains the model between calls, but differs:
- with ``warm_start`` the parameters change and the data is constant
- across calls to ``fit``; with ``partial_fit``, the mini-batch of data
- changes and model parameters stay fixed.
+ with ``warm_start`` the parameters change and the data is
+ (more-or-less) constant across calls to ``fit``; with ``partial_fit``,
+ the mini-batch of data changes and model parameters stay fixed.
+
+ There are cases where you want to use ``warm_start`` to fit on
+ different, but closely related data. For example, one may initially fit
+ to a subset of the data, then fine-tune the parameter search on the
+ full dataset. For classification, all data in a sequence of
+ ``warm_start`` calls to ``fit`` must include samples from each class.
.. _glossary_attributes:
