[Altair] Sync exported histogram code with new bin determination (#304)

* Merge upstream

* Sync with master

* Fix bin size variance from #217

* Format and test

* Change labelOverlap to True

Co-authored-by: Dominik Moritz <domoritz@gmail.com>

* Modify markbar; currently questioning whether or not it's needed

* Remove markbar enitrely, rely on Altair automatic bin detection https://altair-viz.github.io/user_guide/generated/core/altair.BinParams.html

* Modify code snippet

* Revert "Remove markbar enitrely, rely on Altair automatic bin detection https://altair-viz.github.io/user_guide/generated/core/altair.BinParams.html"

This reverts commit 9cb9418.

* Implement bin size estimation via Freedman Diaconis's Rule

* Use numpy to compute IQR for better performance (pandas too slow)

* Add tests

* Add test cases for histogram binning

* Address changes from @domoritz review (small optimizations)

* Black and format

* Move histogram bin width computation to pandas executor (execute_binning)

* Center bars between ticks in distribution setting

* Renaming in execute_binning

* Bin width computed accurately in execute_binning; no need for get_bin_size()

* Revert to Freedman rule; maintain correct ticks

* Sync exported code with new histogram bin determination rules

* Sync exported code with new histogram bin determination rules

* Modify histogram code test case

Co-authored-by: Micah Yong <micahyong@Micahs-MacBook-Pro.local>
Co-authored-by: Dominik Moritz <domoritz@gmail.com>

lux/vislib/altair/Histogram.py

@@ -88,7 +88,8 @@ def initialize_chart(self):
                     y=alt.Y(
                         str(msr_attr.attribute),
                         title=axis_title,
-                        bin=alt.Bin(binned=True, step=markbar),
+                        bin=alt.Bin(binned=True, step=step),
+                        type=msr_attr.data_type,
                         axis=alt.Axis(title=axis_title),
                     ),
                     y2=end_attr_abv,
@@ -99,20 +100,21 @@ def initialize_chart(self):
         #####################################
 
         self.code += "import altair as alt\n"
-        # self.code += f"visData = pd.DataFrame({str(self.data.to_dict(orient='records'))})\n"
         self.code += f"visData = pd.DataFrame({str(self.data.to_dict())})\n"
         if measure.channel == "x":
             self.code += f"""
-		chart = alt.Chart(visData).mark_bar(size={markbar}).encode(
-		    alt.X('{msr_attr.attribute}', title='{axis_title}',bin=alt.Bin(binned=True), type='{msr_attr.data_type}', axis=alt.Axis(labelOverlap=True, title='{axis_title}'), scale=alt.Scale(domain=({x_min}, {x_max}))),
-		    alt.Y("Number of Records", type="quantitative")
+		chart = alt.Chart(visData).mark_bar().encode(
+		    x=alt.X('{msr_attr.attribute}', title='{axis_title}',bin=alt.Bin(binned=True, step={step}), type='{msr_attr.data_type}', axis=alt.Axis(labelOverlap=True, title='{axis_title}'), scale=alt.Scale(domain=({x_min}, {x_max}))),
+            x2='{end_attr_abv}',
+		    y=alt.Y("Number of Records", type="quantitative")
 		)
 		"""
         elif measure.channel == "y":
             self.code += f"""
-		chart = alt.Chart(visData).mark_bar(size={markbar}).encode(
-		    alt.Y('{msr_attr.attribute}', title='{axis_title}',bin=alt.Bin(binned=True), type='{msr_attr.data_type}', axis=alt.Axis(labelOverlap=True, title='{axis_title}'), scale=alt.Scale(domain=({x_min}, {x_max}))),
-		    alt.X("Number of Records", type="quantitative")
+		chart = alt.Chart(visData).mark_bar().encode(
+		    y=alt.Y('{msr_attr.attribute}', title='{axis_title}', bin=alt.Bin(binned=True, step={step}), type='{msr_attr.data_type}', axis=alt.Axis(labelOverlap=True, title='{axis_title}')),
+            y2='{end_attr_abv}',
+		    x=alt.X("Number of Records", type="quantitative")
 		)
 		"""
         return chart

tests/test_vis.py

@@ -17,7 +17,6 @@
 import pandas as pd
 from lux.vis.VisList import VisList
 from lux.vis.Vis import Vis
-from lux.vislib.altair.Histogram import compute_bin_width
 
 
 def test_vis(global_var):
@@ -341,11 +340,9 @@ def test_histogram_chart(global_var):
     lux.config.plotting_backend = "vegalite"
     vis = Vis(["Displacement"], df)
     vis_code = vis.to_Altair()
-    expected_bin_size = compute_bin_width(vis.data["Displacement"])
     assert "alt.Chart(visData).mark_bar" in vis_code
-    assert str(expected_bin_size) in vis_code
     assert (
-        "alt.X('Displacement', title='Displacement (binned)',bin=alt.Bin(binned=True), type='quantitative', axis=alt.Axis(labelOverlap=True, title='Displacement (binned)'), scale=alt.Scale(domain=(68.0, 455.0)))"
+        "alt.X('Displacement', title='Displacement (binned)',bin=alt.Bin(binned=True, step=38.7), type='quantitative', axis=alt.Axis(labelOverlap=True, title='Displacement (binned)'), scale=alt.Scale(domain=(68.0, 455.0)))"
         in vis_code
     )
     assert 'alt.Y("Number of Records", type="quantitative")' in vis_code