Candlestick Chart

A candlestick chart inspired from Protovis (http://mbostock.github.io/protovis/ex/candlestick.html). This example shows the performance of the Chicago Board Options Exchange Volatility Index (VIX) in the summer of 2009. The thick bar represents the opening and closing prices, while the thin bar shows intraday high and low prices; if the index closed higher on a given day, the bars are colored green rather than red.

import altair as alt
import pandas as pd

df = pd.DataFrame(
[
      {
        "date": "2009-06-01",
        "open": 28.7,
        "high": 30.05,
        "low": 28.45,
        "close": 30.04,
        "signal": "short",
        "ret": -4.89396411092985
      },
      {
        "date": "2009-06-02",
        "open": 30.04,
        "high": 30.13,
        "low": 28.3,
        "close": 29.63,
        "signal": "short",
        "ret": -0.322580645161295
      },
      {
        "date": "2009-06-03",
        "open": 29.62,
        "high": 31.79,
        "low": 29.62,
        "close": 31.02,
        "signal": "short",
        "ret": 3.68663594470045
      },
      {
        "date": "2009-06-04",
        "open": 31.02,
        "high": 31.02,
        "low": 29.92,
        "close": 30.18,
        "signal": "short",
        "ret": 4.51010886469673
      },
      {
        "date": "2009-06-05",
        "open": 29.39,
        "high": 30.81,
        "low": 28.85,
        "close": 29.62,
        "signal": "short",
        "ret": 6.08424336973478
      },
      {
        "date": "2009-06-08",
        "open": 30.84,
        "high": 31.82,
        "low": 26.41,
        "close": 29.77,
        "signal": "short",
        "ret": 1.2539184952978
      },
      {
        "date": "2009-06-09",
        "open": 29.77,
        "high": 29.77,
        "low": 27.79,
        "close": 28.27,
        "signal": "short",
        "ret": -5.02431118314424
      },
      {
        "date": "2009-06-10",
        "open": 26.9,
        "high": 29.74,
        "low": 26.9,
        "close": 28.46,
        "signal": "short",
        "ret": -5.46623794212217
      },
      {
        "date": "2009-06-11",
        "open": 27.36,
        "high": 28.11,
        "low": 26.81,
        "close": 28.11,
        "signal": "short",
        "ret": -8.3743842364532
      },
      {
        "date": "2009-06-12",
        "open": 28.08,
        "high": 28.5,
        "low": 27.73,
        "close": 28.15,
        "signal": "short",
        "ret": -5.52763819095477
      },
      {
        "date": "2009-06-15",
        "open": 29.7,
        "high": 31.09,
        "low": 29.64,
        "close": 30.81,
        "signal": "long",
        "ret": 3.4920634920635
      },
      {
        "date": "2009-06-16",
        "open": 30.81,
        "high": 32.75,
        "low": 30.07,
        "close": 32.68,
        "signal": "short",
        "ret": 0.155038759689914
      },
      {
        "date": "2009-06-17",
        "open": 31.19,
        "high": 32.77,
        "low": 30.64,
        "close": 31.54,
        "signal": "short",
        "ret": 5.82822085889571
      },
      {
        "date": "2009-06-18",
        "open": 31.54,
        "high": 31.54,
        "low": 29.6,
        "close": 30.03,
        "signal": "short",
        "ret": 8.17610062893082
      },
      {
        "date": "2009-06-19",
        "open": 29.16,
        "high": 29.32,
        "low": 27.56,
        "close": 27.99,
        "signal": "short",
        "ret": 8.59872611464968
      },
      {
        "date": "2009-06-22",
        "open": 30.4,
        "high": 32.05,
        "low": 30.3,
        "close": 31.17,
        "signal": "short",
        "ret": 15.4907975460123
      },
      {
        "date": "2009-06-23",
        "open": 31.3,
        "high": 31.54,
        "low": 27.83,
        "close": 30.58,
        "signal": "short",
        "ret": 11.7370892018779
      },
      {
        "date": "2009-06-24",
        "open": 30.58,
        "high": 30.58,
        "low": 28.79,
        "close": 29.05,
        "signal": "long",
        "ret": -10.4234527687296
      },
      {
        "date": "2009-06-25",
        "open": 29.45,
        "high": 29.56,
        "low": 26.3,
        "close": 26.36,
        "signal": "long",
        "ret": 0
      },
      {
        "date": "2009-06-26",
        "open": 27.09,
        "high": 27.22,
        "low": 25.76,
        "close": 25.93,
        "signal": "long",
        "ret": 0
      },
      {
        "date": "2009-06-29",
        "open": 25.93,
        "high": 27.18,
        "low": 25.29,
        "close": 25.35,
        "signal": "long",
        "ret": 5.26315789473684
      },
      {
        "date": "2009-06-30",
        "open": 25.36,
        "high": 27.38,
        "low": 25.02,
        "close": 26.35,
        "signal": "long",
        "ret": 6.73758865248228
      }
    ]
)
open_close_color = alt.condition("datum.open < datum.close",
                                 alt.value("#06982d"),
                                 alt.value("#ae1325"))

rule = alt.Chart(df).mark_rule().encode(
    alt.X(
        'yearmonthdate(date):T',
        scale=alt.Scale(domain=[{"month": 5, "date": 31, "year": 2009},
                                {"month": 7, "date": 1, "year": 2009}]),
        axis=alt.Axis(format='%m/%d', title='Date in 2009')
    ),
    alt.Y(
        'low',
        scale=alt.Scale(zero=False),
        axis=alt.Axis(title='Price')
    ),
    alt.Y2('high'),
    color=open_close_color
)

bar = alt.Chart(df).mark_bar().encode(
    x='yearmonthdate(date):T',
    y='open',
    y2='close',
    color=open_close_color
)

rule + bar