update docs with opt. cluster variables

Author: JanTeichertKluge

doc/guide/data/base_data.rst

@@ -183,7 +183,8 @@ To specify the data and the variables for the causal model from arrays we call
       obj_dml_data_sim = double_ml_data_from_matrix(X = X, y = y, d = d)
       obj_dml_data_sim
 
-Cluster assignments can be supplied through the optional ``cluster_vars`` argument (``cluster_cols`` in R).
+In Python, cluster assignments can be supplied through the optional ``cluster_cols`` argument (or ``cluster_vars`` in the ``from_arrays`` method).
+In R, one has to create a ``DoubleMLClusterData`` object instead of ``DoubleMLData`` to use clustering.
 
 .. tab-set::
 
@@ -195,3 +196,5 @@ Cluster assignments can be supplied through the optional ``cluster_vars`` argume
       cluster_vars = (np.arange(n_obs) // 5).reshape(-1, 1)
       obj_dml_data_sim_cluster = DoubleMLData.from_arrays(X, y, d, cluster_vars=cluster_vars)
       obj_dml_data_sim_cluster.cluster_cols
+      print(obj_dml_data_sim_cluster)
+

doc/guide/data/panel_data.rst

@@ -1,6 +1,6 @@
 The ``DoubleMLPanelData`` class serves as data-backend for :ref:`DiD models <did-models>` and can be initialized from a dataframe.
 The class is a subclass of :ref:`DoubleMLData <dml_data>` and inherits all methods and attributes.
-Furthermore, it provides additional methods and attributes to handle panel data ()
+Furthermore, it provides additional methods and attributes to handle panel data.
 
 Key arguments
 """""""""""""

doc/guide/data/ssm_data.rst

@@ -1,14 +1,12 @@
-The ``DoubleMLSSMData`` class covers the sample selection model backend. It
-extends :ref:`DoubleMLData <dml_data>` with a dedicated selection indicator and
-inherits support for clustered data.
+The ``DoubleMLSSMData`` class covers the sample selection model backend. 
+It extends :ref:`DoubleMLData <dml_data>` with a dedicated selection indicator and inherits support for clustered data.
 
 Key arguments
 """""""""""""
 
 * ``s_col``: column containing the selection indicator.
 * ``cluster_cols``: optional cluster identifiers.
-* ``from_arrays``: expects an additional ``s`` array together with ``x``, ``y``
-  and ``d``.
+* ``from_arrays``: expects an additional ``s`` array together with ``x``, ``y`` and ``d``.
 
 The object exposes the ``s`` property and keeps the selection indicator
 separate from covariates and treatment variables.