DOC: Added auto solver table under Ridge Regression in Linear Models
@@ -126,6 +126,23 @@ its ``coef_`` member::
>>> reg.intercept_
0.13636...
+Note that the class :class:`Ridge` allows for the user to specify that the
+solver be automatically chosen by setting `solver="auto"`. When this option
+is specified, :class:`Ridge` will choose between the `"lbfgs"`, `"cholesky"`,
+and `"sparse_cg"` solvers. :class:`Ridge` will begin checking the conditions
+shown in the following table from top to bottom. If the condition is true,
+the corresponding solver is chosen.
+
++-------------+----------------------------------------------------+
+| **Solver** | **Condition** |
++-------------+----------------------------------------------------+
+| 'lbfgs' | The ``positive=True`` option is specified. |
++-------------+----------------------------------------------------+
+| 'cholesky' | The input array X is not sparse. |
++-------------+----------------------------------------------------+
+| 'sparse_cg' | None of the above conditions are fulfilled. |
++-------------+----------------------------------------------------+
+
Classification
--------------
