Make spirals more awesome

Author: sfc-gh-tteixeira

streamlit_app.py

@@ -1,38 +1,40 @@
-from collections import namedtuple
 import altair as alt
-import math
+import numpy as np
 import pandas as pd
 import streamlit as st
 
 """
 # Welcome to Streamlit!
 
-Edit `/streamlit_app.py` to customize this app to your heart's desire :heart:
-
+Edit `/streamlit_app.py` to customize this app to your heart's desire :heart:.
 If you have any questions, checkout our [documentation](https://docs.streamlit.io) and [community
 forums](https://discuss.streamlit.io).
 
 In the meantime, below is an example of what you can do with just a few lines of code:
 """
 
-
-with st.echo(code_location='below'):
-    total_points = st.slider("Number of points in spiral", 1, 5000, 2000)
-    num_turns = st.slider("Number of turns in spiral", 1, 100, 9)
-
-    Point = namedtuple('Point', 'x y')
-    data = []
-
-    points_per_turn = total_points / num_turns
-
-    for curr_point_num in range(total_points):
-        curr_turn, i = divmod(curr_point_num, points_per_turn)
-        angle = (curr_turn + 1) * 2 * math.pi * i / points_per_turn
-        radius = curr_point_num / total_points
-        x = radius * math.cos(angle)
-        y = radius * math.sin(angle)
-        data.append(Point(x, y))
-
-    st.altair_chart(alt.Chart(pd.DataFrame(data), height=500, width=500)
-        .mark_circle(color='#0068c9', opacity=0.5)
-        .encode(x='x:Q', y='y:Q'))
+num_points = st.slider("Number of points in spiral", 1, 10000, 1100)
+num_turns = st.slider("Number of turns in spiral", 1, 300, 31)
+
+indices = np.linspace(0, 1, num_points)
+theta = 2 * np.pi * num_turns * indices
+radius = indices
+
+x = radius * np.cos(theta)
+y = radius * np.sin(theta)
+
+df = pd.DataFrame({
+    "x": x,
+    "y": y,
+    "idx": indices,
+    "rand": np.random.randn(num_points),
+})
+
+st.altair_chart(alt.Chart(df, height=700, width=700)
+    .mark_point(filled=True)
+    .encode(
+        x=alt.X("x", axis=None),
+        y=alt.Y("y", axis=None),
+        color=alt.Color("idx", legend=None, scale=alt.Scale()),
+        size=alt.Size("rand", legend=None, scale=alt.Scale(range=[1, 150])),
+    ))