Merge pull request #553 from eitanlees/horizon-graph

Horizon Graph Example

altair/vegalite/v2/examples/horizon_graph.py

@@ -0,0 +1,38 @@
+"""
+Horizon Graph
+-------------
+This example shows how to make a Horizon Graph with 2 layers. (See https://idl.cs.washington.edu/papers/horizon/ for more details on Horizon Graphs.)
+"""
+
+import altair as alt
+import pandas as pd
+
+df = pd.DataFrame([
+      {"x": 1,  "y": 28}, {"x": 2,  "y": 55},
+      {"x": 3,  "y": 43}, {"x": 4,  "y": 91},
+      {"x": 5,  "y": 81}, {"x": 6,  "y": 53},
+      {"x": 7,  "y": 19}, {"x": 8,  "y": 87},
+      {"x": 9,  "y": 52}, {"x": 10, "y": 48},
+      {"x": 11, "y": 24}, {"x": 12, "y": 49},
+      {"x": 13, "y": 87}, {"x": 14, "y": 66},
+      {"x": 15, "y": 17}, {"x": 16, "y": 27},
+      {"x": 17, "y": 68}, {"x": 18, "y": 16},
+      {"x": 19, "y": 49}, {"x": 20, "y": 15}
+    ])
+
+area1 = alt.Chart(df).mark_area(clip=True, interpolate='monotone').encode(
+    x = alt.X('x', scale=alt.Scale(zero=False, nice=False)), 
+    y = alt.Y('y', scale=alt.Scale(domain=[0, 50]),
+             axis=alt.Axis(title='y')), 
+    opacity = alt.value(0.6)
+).properties(
+    width=300, 
+    height=50
+)
+area2 = alt.Chart(df).mark_area(clip=True, interpolate='monotone').encode(
+    x = 'x',
+    y = alt.Y('ny:Q', scale=alt.Scale(domain=[0, 50])),
+    opacity = alt.value(0.3)
+).transform_calculate("ny", "datum.y - 50")
+
+chart = area1 + area2