ENH Map positions to sectors, calculate sector exposures, plot sector…

… exposures

pyfolio/plotting.py

@@ -921,6 +921,46 @@ def show_and_plot_top_positions(returns, positions_alloc,
         return ax
 
 
+def plot_sector_allocations(returns, sector_alloc, ax=None, **kwargs):
+    """Plots the sector exposures of the portfolio over time.
+
+    Parameters
+    ----------
+    returns : pd.Series
+        Daily returns of the strategy, noncumulative.
+         - See full explanation in tears.create_full_tear_sheet.
+    sector_alloc : pd.DataFrame
+        Portfolio allocation of positions. See pos.get_sector_alloc.
+    ax : matplotlib.Axes, optional
+        Axes upon which to plot.
+    **kwargs, optional
+        Passed to plotting function.
+
+    Returns
+    -------
+    ax : matplotlib.Axes, conditional
+        The axes that were plotted on.
+    """
+    if ax is None:
+        ax = plt.gcf()
+
+    sector_alloc.plot(title='Sector Allocation Over Time',
+                      alpha=0.4, ax=ax, **kwargs)
+
+    box = ax.get_position()
+    ax.set_position([box.x0, box.y0 + box.height * 0.1,
+                     box.width, box.height * 0.9])
+
+    # Put a legend below current axis
+    ax.legend(
+        loc='upper center', frameon=True, bbox_to_anchor=(
+            0.5, -0.14), ncol=5)
+
+    df_cum_rets = timeseries.cum_returns(returns, starting_value=1)
+    ax.set_xlim((df_cum_rets.index[0], df_cum_rets.index[-1]))
+    ax.set_ylabel('Exposure by sector')
+
+
 def plot_return_quantiles(returns, df_weekly, df_monthly, ax=None, **kwargs):
     """Creates a box plot of daily, weekly, and monthly return
     distributions.

pyfolio/pos.py

@@ -15,6 +15,8 @@
 from __future__ import division
 
 import pandas as pd
+import numpy as np
+import warnings
 
 
 def get_percent_alloc(values):
@@ -163,3 +165,38 @@ def get_turnover(transactions, positions, period=None):
     turnover = traded_value / 2.0
     turnover_rate = turnover / portfolio_value
     return turnover_rate
+
+
+def get_sector_exposures(positions, symbol_sector_map):
+    """
+    Sum position exposures by sector.
+
+    Parameters
+    ----------
+    positions : pd.DataFrame
+        Contains position values or amounts.
+    symbol_sector_map : dict or pd.Series
+        Security identifier to sector mapping.
+        Security ids as keys/index, sectors as values.
+
+    Returns
+    -------
+    positions_alloc : pd.DataFrame
+        Sectors and their allocations.
+    """
+    cash = positions.pop('cash')
+
+    unmapped_pos = np.setdiff1d(positions.columns.values,
+                                symbol_sector_map.keys())
+    if len(unmapped_pos) > 0:
+        warn_message = """Warning: Symbols {} have no sector mapping.
+        They will not be included in sector allocations""".format(
+            " ".join(map(str, unmapped_pos)))
+        warnings.warn(warn_message, UserWarning)
+
+    sector_exp = positions.groupby(
+        by=symbol_sector_map, axis=1).sum()
+
+    sector_exp['cash'] = cash
+
+    return sector_exp

pyfolio/tears.py

@@ -42,6 +42,7 @@ def create_full_tear_sheet(returns, positions=None, transactions=None,
                            benchmark_rets=None,
                            gross_lev=None,
                            live_start_date=None, bayesian=False,
+                           sector_mappings=None,
                            cone_std=1.0, set_context=True):
     """
     Generate a number of tear sheets that are useful
@@ -125,6 +126,7 @@ def create_full_tear_sheet(returns, positions=None, transactions=None,
     if positions is not None:
         create_position_tear_sheet(returns, positions,
                                    gross_lev=gross_lev,
+                                   sector_mappings=sector_mappings,
                                    set_context=set_context)
 
         if transactions is not None:
@@ -301,7 +303,7 @@ def create_returns_tear_sheet(returns, live_start_date=None,
 @plotting_context
 def create_position_tear_sheet(returns, positions, gross_lev=None,
                                show_and_plot_top_pos=2,
-                               return_fig=False):
+                               return_fig=False, sector_mappings=None):
     """
     Generate a number of plots for analyzing a
     strategy's positions and holdings.
@@ -328,10 +330,15 @@ def create_position_tear_sheet(returns, positions, gross_lev=None,
         If True, returns the figure that was plotted on.
     set_context : boolean, optional
         If True, set default plotting style context.
+    sector_mapping: dict or pd.Series.
+        Security identifier to sector mapping.
+        Security ids as keys, sectors as values.
     """
 
-    fig = plt.figure(figsize=(14, 4 * 6))
-    gs = gridspec.GridSpec(4, 3, wspace=0.5, hspace=0.5)
+    vertical_sections = 5 if sector_mappings else 4
+
+    fig = plt.figure(figsize=(14, vertical_sections * 6))
+    gs = gridspec.GridSpec(vertical_sections, 3, wspace=0.5, hspace=0.5)
     ax_gross_leverage = plt.subplot(gs[0, :])
     ax_exposures = plt.subplot(gs[1, :], sharex=ax_gross_leverage)
     ax_top_positions = plt.subplot(gs[2, :], sharex=ax_gross_leverage)
@@ -352,6 +359,15 @@ def create_position_tear_sheet(returns, positions, gross_lev=None,
 
     plotting.plot_holdings(returns, positions_alloc, ax=ax_holdings)
 
+    if sector_mappings is not None:
+        sector_exposures = pos.get_sector_exposures(positions, sector_mappings)
+
+        sector_alloc = pos.get_percent_alloc(sector_exposures)
+        sector_alloc = sector_alloc.drop('cash', axis='columns')
+        ax_sector_alloc = plt.subplot(gs[4, :], sharex=ax_gross_leverage)
+        plotting.plot_sector_allocations(returns, sector_alloc,
+                                         ax=ax_sector_alloc)
+
     plt.show()
     if return_fig:
         return fig

pyfolio/tests/test_pos.py

@@ -1,4 +1,5 @@
 from unittest import TestCase
+from nose_parameterized import parameterized
 from collections import OrderedDict
 
 from pandas import (
@@ -17,10 +18,13 @@
 
 from pyfolio.pos import (get_percent_alloc,
                          extract_pos,
-                         get_turnover)
+                         get_turnover,
+                         get_sector_exposures)
+import warnings
 
 
 class PositionsTestCase(TestCase):
+    dates = date_range(start='2015-01-01', freq='D', periods=20)
 
     def test_get_percent_alloc(self):
         raw_data = arange(15, dtype=float).reshape(5, 3)
@@ -121,3 +125,41 @@ def test_get_turnover(self):
         result = get_turnover(transactions, positions, period='M')
         expected = Series([10.0], index=index)
         assert_series_equal(result, expected)
+
+    @parameterized.expand([
+        (DataFrame([[1.0, 2.0, 3.0, 10.0]]*len(dates),
+                   columns=[0, 1, 2, 'cash'], index=dates),
+         {0: 'A', 1: 'B', 2: 'A'},
+         DataFrame([[4.0, 2.0, 10.0]]*len(dates),
+                   columns=['A', 'B', 'cash'], index=dates),
+         False),
+        (DataFrame([[1.0, 2.0, 3.0, 10.0]]*len(dates),
+                   columns=[0, 1, 2, 'cash'], index=dates),
+         Series(index=[0, 1, 2], data=['A', 'B', 'A']),
+         DataFrame([[4.0, 2.0, 10.0]]*len(dates),
+                   columns=['A', 'B', 'cash'], index=dates),
+         False),
+        (DataFrame([[1.0, 2.0, 3.0, 10.0]]*len(dates),
+                   columns=[0, 1, 2, 'cash'], index=dates),
+         {0: 'A', 1: 'B'},
+         DataFrame([[1.0, 2.0, 10.0]]*len(dates),
+                   columns=['A', 'B', 'cash'], index=dates),
+         True)
+    ])
+    def test_sector_exposure(self, positions, mapping,
+                             expected_sector_exposure,
+                             warning_expected):
+        """
+        Tests sector exposure mapping and rollup.
+
+        """
+        with warnings.catch_warnings(record=True) as w:
+            result_sector_exposure = get_sector_exposures(positions,
+                                                          mapping)
+
+            assert_frame_equal(result_sector_exposure,
+                               expected_sector_exposure)
+            if warning_expected:
+                assert len(w) == 1
+            else:
+                assert len(w) == 0