Comparative Analysis

It is often useful to compare the performance of different index methods. We will demonstrate how to do this by comparing metrics and visualizing the indices.

Basic Setup

First, we will load some sales data and create several different indices:

>>> from hpipy.datasets import load_seattle_sales
>>> from hpipy.extensions import NeuralNetworkIndex, RandomForestIndex
>>> from hpipy.price_index import HedonicIndex, RepeatTransactionIndex

>>> df = load_seattle_sales()

>>> index_kwargs = {
...     "trans_data": df,
...     "prop_id": "pinx",
...     "trans_id": "sale_id",
...     "price": "sale_price",
...     "date": "sale_date",
...     "periodicity": "M",
... }
>>> rt_kwargs = {
...     **index_kwargs,
...     "estimator": "robust",
...     "log_dep": True,
... }
>>> hed_kwargs = {
...     **index_kwargs,
...     "dep_var": "price",
...     "ind_var": ["tot_sf", "beds", "baths"],
... }

>>> hpi_rt = RepeatTransactionIndex.create_index(**rt_kwargs)
>>> hpi_hed = HedonicIndex.create_index(**hed_kwargs)
>>> hpi_rf = RandomForestIndex.create_index(**hed_kwargs)
>>> hpi_nn = NeuralNetworkIndex.create_index(**hed_kwargs, preprocess_geo=False)

>>> indices = [hpi_rt, hpi_hed, hpi_rf, hpi_nn]

Comparing Metrics

Compare metrics between different index methods:

>>> import pandas as pd
>>> from hpipy.utils.metrics import volatility

>>> df_mean_vol = pd.DataFrame(
...    {
...        "Index": [idx.__class__.__name__ for idx in indices],
...        "Volatility": [volatility(idx)["mean"].iloc[0] for idx in indices],
...    }
... )

>>> df_mean_vol.sort_values(by="Volatility").round(3)
                    Index  Volatility
3      NeuralNetworkIndex       0.009
2       RandomForestIndex       0.014
0  RepeatTransactionIndex       0.017
1            HedonicIndex       0.023

Visualizing Indices

Visualize different index methods:

>>> import altair as alt
>>> from hpipy.utils.plotting import plot_index

>>> alt.layer(
...     (
...         plot_index(hpi_rt)
...         .transform_calculate(method="'Repeat Sales'")
...         .encode(color=alt.Color("method:N", title="Method"))
...     ),
...     (
...         plot_index(hpi_hed)
...         .transform_calculate(method="'Hedonic Pricing'")
...         .encode(color=alt.Color("method:N", title="Method"))
...     ),
...     (
...         plot_index(hpi_rf)
...         .transform_calculate(method="'Random Forest'")
...         .encode(color=alt.Color("method:N", title="Method"))
...     ),
...     (
...         plot_index(hpi_nn)
...         .transform_calculate(method="'Neural Network'")
...         .encode(color=alt.Color("method:N", title="Method"))
...     ),
... ).properties(title="Price Index Method Comparison")
alt.LayerChart(...)