add more documentation on new arc mark

doc/user_guide/compound_charts.rst

@@ -270,8 +270,24 @@ The :meth:`Chart.repeat` method is the key here: it lets you specify a set of
 encodings for the row and/or column which can be referred to in the chart's
 encoding specification using ``alt.repeat('row')`` or ``alt.repeat('column')``.
 
-Currently ``repeat`` can only be specified for rows and column (not, e.g., for
-layers) and the target can only be encodings (not, e.g., data transforms)
+Another option to use the ``repeat`` method is for layering. Here below the
+columns ``US_Gross`` and ``Worldwide_Gross`` are layered on the ``y``-axis
+using ``alt.repeat('layer')``: 
+
+.. altair-plot::
+
+    import altair as alt
+    from vega_datasets import data
+
+    source = data.movies()
+
+    alt.Chart(source).mark_line().encode(
+        x=alt.X("IMDB_Rating", bin=True),
+        y=alt.Y(alt.repeat('layer'), aggregate='mean', title="Mean of US and Worldwide Gross"),
+        color=alt.ColorDatum(alt.repeat('layer'))
+    ).repeat(layer=["US_Gross", "Worldwide_Gross"])
+
+Currently ``repeat`` can only be encodings (not, e.g., data transforms)
 but there is discussion within the Vega-Lite community about making this pattern
 more general in the future.
 

doc/user_guide/encoding.rst

@@ -57,6 +57,8 @@ xError      :class:`XError`      The x-axis error value             N/A
 yError      :class:`YError`      The y-axis error value             N/A
 xError2     :class:`XError2`     The second x-axis error value      N/A
 yError2     :class:`YError2`     The second y-axis error value      N/A
+theta       :class:`Theta`       The start arc angle                :ref:`gallery_radial_chart`
+theta2      :class:`Theta2`      The end arc angle (radian)         :ref:`gallery_pacman_chart`
 ==========  ===================  =================================  ===================================
 
 Mark Property Channels:
@@ -68,6 +70,7 @@ color          :class:`Color`          The color of the mark           :ref:`gal
 fill           :class:`Fill`           The fill for the mark           :ref:`gallery_ridgeline_plot`
 fillopacity    :class:`FillOpacity`    The opacity of the mark's fill  N/A
 opacity        :class:`Opacity`        The opacity of the mark         :ref:`gallery_horizon_graph`
+radius         :class:`Radius`         The radius or the mark          :ref:`gallery_radial_chart`
 shape          :class:`Shape`          The shape of the mark           :ref:`gallery_us_incomebrackets_by_state_facet`
 size           :class:`Size`           The size of the mark            :ref:`gallery_table_bubble_plot_github`
 stroke         :class:`Stroke`         The stroke of the mark          N/A

doc/user_guide/marks.rst

@@ -15,6 +15,7 @@ Altair provides a number of basic mark properties:
 ==========  ============================  ===================================================  ====================================
 Mark Name   Method                        Description                                          Example
 ==========  ============================  ===================================================  ====================================
+arc         :meth:`~Chart.mark_arc`       A pie chart.                                         :ref:`gallery_pie_chart`
 area        :meth:`~Chart.mark_area`      A filled area plot.                                  :ref:`gallery_simple_stacked_area_chart`
 bar         :meth:`~Chart.mark_bar`       A bar plot.                                          :ref:`gallery_simple_bar_chart`
 circle      :meth:`~Chart.mark_circle`    A scatter plot with filled circles.                  :ref:`gallery_one_dot_per_zipcode`