{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Markov Variance Switching\n", "\n", "Kim, C., Nelson, C., and Startz, R. (1998). Testing for mean reversion in heteroskedastic data based on Gibbs-sampling-augmented randomization. Journal of Empirical Finance, (5)2, pp.131-154.\n", "\n", "**Author:** shittles\n", "\n", "**Created:** 2024-09-18\n", "\n", "**Modified:** 2024-09-19\n", "\n", "## Changelog\n" ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [], "source": [ "import ray\n", "import numpy as np\n", "import pandas as pd\n", "import plotly.express as px\n", "import plotly.graph_objects as go\n", "import statsmodels.api as sm\n", "\n", "from sklearn.compose import make_column_transformer\n", "from sklearn.preprocessing import RobustScaler\n", "\n", "from vectorbtpro import *" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "ray.init()" ] }, { "cell_type": "code", "execution_count": 3, "metadata": {}, "outputs": [], "source": [ "vbt.settings.set_theme(\"dark\")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Ingestion\n" ] }, { "cell_type": "code", "execution_count": 4, "metadata": {}, "outputs": [], "source": [ "symbol = \"^GSPC\" # the S&P 500 ticker" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "data = vbt.YFData.pull(\n", " symbol, start=\"50 years ago\", end=\"today\", timeframe=\"daily\", tz=\"UTC\"\n", ") # 50 years of data\n", "\n", "data.stats()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "data.data[symbol]" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "data.data[symbol].index" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# The opens are corrupt...\n", "data.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# but the closes are fine.\n", "data.data[\"^GSPC\"][\"Close\"].vbt.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Cleaning\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "data.data[symbol][\"Dividends\"].any()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "data.data[symbol][\"Stock Splits\"].any()" ] }, { "cell_type": "code", "execution_count": 12, "metadata": {}, "outputs": [], "source": [ "data = data.remove_features([\"Dividends\", \"Stock Splits\"])" ] }, { "cell_type": "code", "execution_count": 13, "metadata": {}, "outputs": [], "source": [ "# data = data.transform(lambda df: df.loc[\"April 19th 1982\" < df.index])" ] }, { "cell_type": "code", "execution_count": 14, "metadata": {}, "outputs": [], "source": [ "# data.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": 15, "metadata": {}, "outputs": [], "source": [ "# len(data.index) / 365.25 # 30 years of data remaining" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Modelling\n" ] }, { "cell_type": "code", "execution_count": 16, "metadata": {}, "outputs": [], "source": [ "# sr_open = data.get(\"Open\")\n", "# sr_high = data.get(\"High\")\n", "# sr_low = data.get(\"Low\")\n", "sr_close = data.get(\"Close\")" ] }, { "cell_type": "code", "execution_count": 17, "metadata": {}, "outputs": [], "source": [ "# sr_log_open = np.log(sr_open)\n", "# sr_log_high = np.log(sr_high)\n", "# sr_log_low = np.log(sr_low)\n", "sr_log_close = np.log(sr_close)" ] }, { "cell_type": "code", "execution_count": 18, "metadata": {}, "outputs": [], "source": [ "sr_log_returns = data.log_returns" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "sr_log_returns.vbt.plot().show()" ] }, { "cell_type": "code", "execution_count": 20, "metadata": {}, "outputs": [], "source": [ "column_transformer = make_column_transformer(\n", " (RobustScaler(), [symbol]),\n", ")\n", "\n", "sr_log_returns_scaled = pd.Series(\n", " data=column_transformer.fit_transform(pd.DataFrame(sr_log_returns)).ravel(),\n", " index=sr_log_returns.index,\n", ")" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "sr_log_returns_scaled.vbt.plot().show()" ] }, { "cell_type": "code", "execution_count": 22, "metadata": {}, "outputs": [], "source": [ "k_regimes_kns = 3" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "kns = sm.tsa.MarkovRegression(\n", " sr_log_returns_scaled, k_regimes=k_regimes_kns, trend=\"n\", switching_variance=True\n", ")\n", "results_kns = kns.fit()\n", "\n", "results_kns.summary()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "results_kns.filtered_marginal_probabilities # using data until time t (excluding time t+1, ..., T)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "results_kns.smoothed_marginal_probabilities # using data until time T" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "fig = vbt.make_subplots(\n", " rows=k_regimes_kns,\n", " cols=1,\n", " y_title=\"Smoothed Marginal Variance Regime Probabilities\",\n", " shared_xaxes=True,\n", " subplot_titles=[\n", " \"Medium-variance\",\n", " \"Low-variance\",\n", " \"High-variance\",\n", " ], # order changes dependent on fit\n", ")\n", "\n", "for i in range(k_regimes_kns):\n", " fig = results_kns.smoothed_marginal_probabilities[i].vbt.plot(\n", " add_trace_kwargs=dict(row=i + 1, col=1), fig=fig\n", " )\n", "\n", "\n", "fig.update_layout(showlegend=False)\n", "fig.show()" ] }, { "cell_type": "code", "execution_count": 27, "metadata": {}, "outputs": [], "source": [ "def plot_annotated_line(\n", " fig: go.Figure,\n", " x: pd.Series,\n", " y: pd.Series,\n", " classes: pd.Series,\n", " dict_class_colours: dict,\n", " dict_class_labels: dict,\n", ") -> go.Figure:\n", " \"\"\"Plot a line chart where each trace is coloured based on its class.\n", "\n", " Yes, plotly really doesn't support this out of the box.\n", "\n", " Args:\n", " fig: Figure.\n", " x: Indices.\n", " y: Close prices.\n", " classes: Regimes.\n", " dict_class_colours: In the format {class: colour}\n", " dict_class_labels: In the format {class: label}\n", "\n", " Returns:\n", " fig: The figure.\n", " \"\"\"\n", " # Plot each segment in its corresponding color.\n", " for i in range(len(x) - 1):\n", " fig.add_trace(\n", " go.Scatter(\n", " x=x[i : i + 2],\n", " y=y[i : i + 2],\n", " mode=\"lines\",\n", " line=dict(color=dict_class_colours[classes[i]], width=2),\n", " showlegend=False, # added manually\n", " )\n", " )\n", "\n", " # Label each regime.\n", " for regime, colour in dict_class_colours.items():\n", " fig.add_trace(\n", " go.Scatter(\n", " x=[None],\n", " y=[None],\n", " mode=\"lines\",\n", " line=dict(color=colour, width=2),\n", " name=dict_class_labels[regime],\n", " )\n", " )\n", "\n", " return fig" ] }, { "cell_type": "code", "execution_count": 28, "metadata": {}, "outputs": [], "source": [ "sr_variance_regime_forecasts = results_kns.filtered_marginal_probabilities.idxmax(\n", " axis=1\n", ")\n", "\n", "sr_variance_regime_predictions = results_kns.smoothed_marginal_probabilities.idxmax(\n", " axis=1\n", ")" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# sr_variance_regime_forecasts.vbt.plot().show()\n", "sr_variance_regime_predictions.vbt.plot().show()" ] }, { "cell_type": "code", "execution_count": 30, "metadata": {}, "outputs": [], "source": [ "# order changes dependent on fit\n", "dict_variance_regime_labels = {\n", " 0: \"Medium\",\n", " 1: \"Low\",\n", " 2: \"High\",\n", "}\n", "\n", "dict_variance_regime_colours = {\n", " 0: \"orange\",\n", " 1: \"green\",\n", " 2: \"red\",\n", "}" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "fig = vbt.make_figure()\n", "\n", "fig = plot_annotated_line(\n", " fig,\n", " data.index,\n", " sr_log_close,\n", " # sr_variance_regime_forecasts.rolling(5).mean().fillna(0).round(0),\n", " sr_variance_regime_forecasts,\n", " # sr_variance_regime_predictions,\n", " dict_variance_regime_colours,\n", " dict_variance_regime_labels,\n", ")\n", "\n", "fig.update_layout(\n", " title=\"Filtered Variance Regime Labels\",\n", " # title=\"Smoothed Variance Regime Labels\",\n", " xaxis_title=\"Date\",\n", " yaxis_title=\"Log Close\",\n", " showlegend=True,\n", ")\n", "\n", "fig.show()" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Backtest\n", "### Filtered marginal probabilities\n", "A backtest using filtered marginal probabilities.\n" ] }, { "cell_type": "code", "execution_count": 32, "metadata": {}, "outputs": [], "source": [ "# TODO - Double check me!\n", "# Assuming that you sell today if yesterday was in the high-variance regime.\n", "# entries = (sr_variance_regime_forecasts != 2).vbt.signals.fshift()\n", "# exits = (sr_variance_regime_forecasts == 2).vbt.signals.fshift()\n", "\n", "# Assuming that you sell today (at the close) if today was in the high-variance regime.\n", "entries = (sr_variance_regime_forecasts != 2)\n", "exits = (sr_variance_regime_forecasts == 2)\n", "\n", "# I haven't tested any additional logic.\n", "# entries = (sr_variance_regime_forecasts.rolling(5).mean().fillna(0).round(0) != 2)\n", "\n", "clean_entries, clean_exits = entries.vbt.signals.clean(exits)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "fig = sr_variance_regime_forecasts.vbt.plot()\n", "\n", "clean_entries.vbt.signals.plot_as_entries(sr_variance_regime_forecasts, fig=fig)\n", "clean_exits.vbt.signals.plot_as_exits(sr_variance_regime_forecasts, fig=fig)\n", "\n", "fig.show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf = vbt.Portfolio.from_signals(\n", " close=sr_close,\n", " entries=clean_entries,\n", " exits=clean_exits,\n", " direction=\"both\",\n", " fees=0.001,\n", " size=1.0,\n", " size_type=vbt.pf_enums.SizeType.ValuePercent,\n", ")\n", "\n", "pf.stats()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.drawdowns.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.plot_underwater(pct_scale=True).show()" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Re-fitting Every Day\n", "A backtest with a single training and validation set, that's refit every day" ] }, { "cell_type": "code", "execution_count": 38, "metadata": {}, "outputs": [], "source": [ "n_days_validation = int(365.25 * 2) # 2 years of data held back for the validation set" ] }, { "cell_type": "code", "execution_count": 39, "metadata": {}, "outputs": [], "source": [ "# slices_sr = vbt.Splitter.split_range(slice(None), new_split=-n_days_validation, index=data.index)\n", "splitter_fr = vbt.Splitter.from_rolling(\n", " data.index, length=len(data.index), split=len(data.index) - n_days_validation\n", ")" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "splitter_fr.plot().show()" ] }, { "cell_type": "code", "execution_count": 41, "metadata": {}, "outputs": [], "source": [ "# Define a Ray remote function for parallelization.\n", "@ray.remote\n", "def compute_smoothed_marginal_probabilities(sr):\n", " kns = sm.tsa.MarkovRegression(\n", " sr,\n", " k_regimes=k_regimes_kns,\n", " trend=\"n\",\n", " switching_variance=True,\n", " )\n", " results_kns = kns.fit()\n", "\n", " # the smoothing might not work properly out of sample\n", " return results_kns.smoothed_marginal_probabilities.iloc[-1]" ] }, { "cell_type": "code", "execution_count": 42, "metadata": {}, "outputs": [], "source": [ "# The predict method doesn't support out of sample forecasts...\n", "# kns = sm.tsa.MarkovRegression(\n", "# sr_log_returns[splitter_fr.get_mask()[\"set_0\"]],\n", "# k_regimes=k_regimes_kns,\n", "# trend=\"n\",\n", "# switching_variance=True,\n", "# )\n", "# results_kns = kns.fit()\n", "\n", "# results_kns.summary()\n", "\n", "# results_kns.predict(sr_log_returns[splitter_fr.get_mask()[\"set_1\"]])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "https://github.com/statsmodels/statsmodels/issues/7982" ] }, { "cell_type": "code", "execution_count": 43, "metadata": {}, "outputs": [], "source": [ "sr_train = sr_log_returns[splitter_fr.get_mask()[\"set_0\"]]\n", "sr_validate = sr_log_returns[splitter_fr.get_mask()[\"set_1\"]]" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# ...so re-fit the model every timestep.\n", "futures = []\n", "\n", "sr_log_returns_to_date = sr_train.copy()\n", "\n", "# launch parallel tasks\n", "for i in range(len(sr_validate)):\n", " sr_log_returns_to_date = pd.concat(\n", " [\n", " sr_log_returns_to_date,\n", " pd.Series(sr_validate.iloc[i], index=[sr_validate.index[i]]),\n", " ]\n", " )\n", "\n", " futures.append(\n", " compute_smoothed_marginal_probabilities.remote(sr_log_returns_to_date)\n", " )\n", "\n", "# collect results\n", "smoothed_marginal_probabilities = ray.get(futures)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "smoothed_marginal_probabilities = pd.concat(smoothed_marginal_probabilities, axis=1).T\n", "\n", "smoothed_marginal_probabilities.index.name = \"Date\"" ] }, { "cell_type": "code", "execution_count": 38, "metadata": {}, "outputs": [], "source": [ "sr_variance_regime_predictions = smoothed_marginal_probabilities.idxmax(\n", " axis=1\n", ")" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "sr_close_validate = sr_close[splitter_fr.get_mask()[\"set_1\"]]\n", "\n", "sr_log_close_validate = sr_log_close[splitter_fr.get_mask()[\"set_1\"]]" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "fig = vbt.make_figure()\n", "\n", "fig = plot_annotated_line(\n", " fig,\n", " data.index[splitter_fr.get_mask()[\"set_1\"]],\n", " sr_log_close_validate,\n", " sr_variance_regime_predictions,\n", " dict_variance_regime_colours,\n", " dict_variance_regime_labels,\n", ")\n", "\n", "fig.update_layout(\n", " title=\"Variance Regime Forecasts\",\n", " xaxis_title=\"Date\",\n", " yaxis_title=\"Log Close\",\n", " showlegend=True,\n", ")\n", "\n", "fig.show()" ] }, { "cell_type": "code", "execution_count": 49, "metadata": {}, "outputs": [], "source": [ "# TODO - Double check me!\n", "# Assuming that you sell today if yesterday was in the high-variance regime.\n", "# entries = (sr_variance_regime_forecasts != 2).vbt.signals.fshift()\n", "# exits = (sr_variance_regime_forecasts == 2).vbt.signals.fshift()\n", "\n", "# Assuming that you sell today (at the close) if today was in the high-variance regime.\n", "entries = (sr_variance_regime_forecasts != 2)\n", "exits = (sr_variance_regime_forecasts == 2)\n", "\n", "# I haven't tested any additional logic.\n", "# entries = (sr_variance_regime_forecasts.rolling(5).mean().fillna(0).round(0) != 2)\n", "\n", "clean_entries, clean_exits = entries.vbt.signals.clean(exits)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "fig = sr_variance_regime_forecasts.vbt.plot()\n", "\n", "clean_entries.vbt.signals.plot_as_entries(sr_variance_regime_forecasts, fig=fig)\n", "clean_exits.vbt.signals.plot_as_exits(sr_variance_regime_forecasts, fig=fig)\n", "\n", "fig.show()" ] }, { "cell_type": "code", "execution_count": 51, "metadata": {}, "outputs": [], "source": [ "pf = vbt.Portfolio.from_signals(\n", " close=sr_close_validate,\n", " entries=clean_entries,\n", " exits=clean_exits,\n", " direction=\"both\",\n", " fees=0.001,\n", " size=1.0,\n", " size_type=vbt.pf_enums.SizeType.ValuePercent,\n", ")" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.stats()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.drawdowns.plot(yaxis=dict(type=\"log\")).show()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "pf.plot_underwater(pct_scale=True).show()" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Observations\n", "- For this implementation you have to use the filtered probabilities to not introduce look-ahead bias.\n", "- If you backtest the smoothed probilities (which smoothes using all of the data) it only performs well after the great financial crisis. Why? No clue.\n", "- It looks like its better for labelling than it is as a strategy in its current state.\n", "- After slow recessions like the dot-com bubble, there can be a medium-variance decline which this simple strategy doesn't capture.\n", "- After fast recessions like covid-19, there can be a high-variance rebound which this simple strategy doesn't capture.\n", "- **It looks like you can safely leverage up during low-variance regimes.**\n", "- Maybe you could combine this strategy with other recession-leading indicators (e.g. manufacturing/services pmi, federal funds rate, 10y-2y yield curve, 1y-3mo yield curve) to help time the tops?\n", "- Maybe you could combine this strategy with another trend-following strategy (e.g. VWAP, EMA, BBANDS, ADX) to help time the bottoms?\n" ] }, { "cell_type": "code", "execution_count": 46, "metadata": {}, "outputs": [], "source": [ "ray.shutdown()" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": ".venv", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.12.0" } }, "nbformat": 4, "nbformat_minor": 2 }