unified additional properties

.gitignore

@@ -102,3 +102,11 @@ venv.bak/
 
 # mypy
 .mypy_cache/
+
+
+# vscode
+.vscode/
+
+# examples
+.examples/
+examples/example.ipynb

altair_pandas/_core.py

@@ -6,6 +6,44 @@ def _valid_column(column_name):
     return str(column_name)
 
 
+def _set_encode(chart, cols, value, attribute, types, alt_obj):
+    '''handles all possible meanings/values of the attribute'''
+    if value in cols:
+        setattr(chart.encoding, attribute, alt_obj(value))
+    elif isinstance(value, alt_obj):
+        setattr(chart.encoding, attribute, value)
+    elif isinstance(value, types):
+        setattr(chart.encoding, attribute, alt.value(value))
+    elif isinstance(value, (pd.Series, pd.np.array)):
+        raise NotImplementedError()
+    else:
+        text = f'Supposed to be either column name, or {types}, or {alt_obj} object'  # noqa
+        raise ValueError(text)
+
+
+def _pass_additional_properties(chart, cols, kwargs):
+    '''make use of additional properties, such as
+    color, title, alpha, etc.
+    '''
+    if 'title' in kwargs:
+        chart.title = kwargs['title']
+
+    if 'color' in kwargs:
+        color = kwargs.get('color')
+        _set_encode(chart, cols, color, 'color', str, alt.Color)
+
+    if 'alpha' in kwargs:
+        alpha = kwargs['alpha']
+        _set_encode(chart,
+                    cols,
+                    alpha,
+                    'opacity',
+                    (int, float),
+                    alt.Opacity)
+
+    return chart
+
+
 class _PandasPlotter:
     """Base class for pandas plotting."""
     @classmethod
@@ -190,4 +228,9 @@ def plot(data, kind='line', **kwargs):
         raise NotImplementedError(
             f"kind='{kind}' for data of type {type(data)}")
 
-    return plotfunc(**kwargs)
+    chart = plotfunc(**kwargs)
+    if isinstance(data, pd.DataFrame):
+        cols = data.columns.tolist()
+    else:
+        cols = [data.name, data.index.name]
+    return _pass_additional_properties(chart, cols, kwargs)

altair_pandas/test_plotting.py

@@ -1,6 +1,7 @@
 import pytest
 import numpy as np
 import pandas as pd
+import altair as alt
 
 
 @pytest.fixture
@@ -141,3 +142,33 @@ def test_dataframe_boxplot(dataframe, with_plotting_backend):
     assert spec['encoding']['x']['field'] == 'column'
     assert spec['encoding']['y']['field'] == 'value'
     assert spec['transform'][0]['fold'] == ['x', 'y']
+
+
+@pytest.mark.parametrize('props', [
+    {'title': 'Test Title', 'color': 'y', 'alpha': 0.2},
+    {'title': 'Test Title', 'color': 'purple', 'alpha': 'y'},
+    {'title': 'Test Title', 'color': 'purple', 'alpha': 'y'},
+    {'title': 'Test Title', 'color': 'purple', 'alpha': 'y'},
+    {'title': 'Test Title',
+     'color': alt.Color('y', scale=alt.Scale(scheme='viridis')),
+     'alpha': 0.2}
+    ])
+def test_additional_properties(dataframe, props, with_plotting_backend):
+    chart = dataframe.plot.barh(**props)
+    spec = chart.to_dict()
+
+    assert spec['title'] == props['title']
+
+    if props['alpha'] == 0.2:
+        assert spec['encoding']['opacity'] == alt.value(props['alpha'])
+    else:
+        assert spec['encoding']['opacity'] == {'field': props['alpha'],
+                                               'type': 'quantitative'}
+
+    if props['color'] == 'purple':
+        assert spec['encoding']['color'] == alt.value(props['color'])
+    elif isinstance(props['color'], alt.Color):
+        assert spec['encoding']['color'] == props['color'].to_dict()
+    else:
+        assert spec['encoding']['color'] == {'field': props['color'],
+                                             'type': 'quantitative'}