nexus-corr-discovery 0.0.3.dev3

Correlation discovery over collections of spatio-temporal datasets

Nexus: Correlation Discovery over Collections of Spatio-Temporal Tabular Data

Install

$ pip install nexus-corr-discovery

Quickstart

We have prepared a quickstart guide for you to learn the basics of Nexus!

Add your own data

This notebook introduces how to incorporate your own data.

Add a data source

In this stage, a data source is added, and Nexus will annotate spatial/temporal and numerical attributes for datasets within this source, storing this information accordingly.

To add a data source, you need to specify the name of the data source, the path to the data and a list of spatial hierarchies. To define a spatial hierarchy, you need to provide a shape file, and the mapping between spatial granularities to the shape file headers. You can also add a data source without specifying a spatial hierarchy if you don't need to convert attributes with geographical coordinate granularity into other granularities.

The data source will be added to config.yaml by default. You could change the path to store data source configurations by doing

$ export CONFIG_FILE_PATH="path_to_your_configuration_file"

As directory containing all the metadata related to that data source will be created at resource/{data source name}.

from nexus.nexus_api import API

spatial_hierarchy1 = SpatialHierarchy('resource/chicago_shapes/shape_chicago_blocks/geo_export_8e927c91-3aad-4b67'
                                          '-86ff-bf4de675094e.shp',
                                          {
                                              SPATIAL_GRANU.BLOCK: 'blockce10',
                                              SPATIAL_GRANU.TRACT: 'tractce10',
                                              SPATIAL_GRANU.COUNTY: 'countyfp10',
                                              SPATIAL_GRANU.STATE: 'statefp10'})

spatial_hierarchy2 = SpatialHierarchy("resource/chicago_shapes/shape_chicago_zipcodes/geo_export_a86acac7-4554"
                                        "-4a8c-b482-7e49844799cf.shp",
                                        {
                                            SPATIAL_GRANU.ZIPCODE: "zip"
                                        })

API.add_data_source(data_source_name='chicago_open_data', 
                    data_path='data/chicago_open_data_1m/', 
                    spatial_hierarchies=[spatial_hierarchy1, spatial_hierarchy2])

Data Ingestion

Once a data source is added, the next step is to ingest data into a database. Nexus supports both DuckDB and Postgres.

To use the api ingest_data, you need to specify the connection to a database, the data sources and the desired spatial/temporal granularities.

from nexus.utils.spatial_hierarchy import SPATIAL_GRANU
from nexus.utils.time_point import TEMPORAL_GRANU

data_sources = ['chicago_open_data']
conn_str = 'data/test.db'
temporal_granu_l = []
spatial_granu_l = [SPATIAL_GRANU.ZIPCODE]
API.ingest_data(conn_str=conn_str, engine='duckdb', data_sources=data_sources,
                temporal_granu_l=temporal_granu_l, spatial_granu_l=spatial_granu_l)

Datasets used in the paper

All datasets used in the Nexus paper can be downloaded here.

Open Data Crawler

If you want to download datasets from open data portals, please refer to nexus/data_prep/opendata_client.py and nexus/data_prep/table_downloader.py.

Create app tokens and api keys on Socrata

Socrata is a platform that manages many open data portals. To use the above scripts, you need to first obtain an API key. Please follow this blog to get the key first https://support.socrata.com/hc/en-us/articles/210138558-Generating-App-Tokens-and-API-Keys

Get all dataset information under an open data portal

You can use OpenDataClient under opendata_client.py to get the catalog of datasets under a portal.

domain = "data.cityofchicago.org"
client = OpenDataClient(domain, "https://data.cityofchicago.org/resource/", "Your App Token")
res = client.datasets(domain)
datasets_to_download = []
for obj in res:
    id = obj['resource']['id']
    name = obj['resource']['name']
    datasets_to_download.append([domain, id])
import json
with open('chicago_open_data.json', 'w') as f:
    json.dump(datasets_to_download, f, indent=4)

Download datasets

table_downloader.py downloads the given datasets in parallel. It takes as input a list of (open data domain, dataset id) pairs.

line_limit = 500000
dataset_dir = f"data/chicago_open_data/" # path to save the downloaded datasets
config = io_utils.load_config("data_prep")
root_dir, app_token = config["root_dir"], config["app_token"]
if not os.path.isdir(dataset_dir):
    os.makedirs(dataset_dir)
data_downloader = TableDownloader(
    output_dir=dataset_dir, app_token=app_token
)
meta_file = 'chicago_open_data.json' # the one we obtained from the previous step with domain name and dataset id.
data_downloader.download_all(line_limit, meta_file)

Citation

@article{10.1145/3654957,
author = {Gong, Yue and Galhotra, Sainyam and Castro Fernandez, Raul},
title = {Nexus: Correlation Discovery over Collections of Spatio-Temporal Tabular Data},
year = {2024},
issue_date = {June 2024},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
volume = {2},
number = {3},
url = {https://doi.org/10.1145/3654957},
doi = {10.1145/3654957},
abstract = {Causal analysis is essential for gaining insights into complex real-world processes and making informed decisions. However, performing accurate causal analysis on observational data is generally infeasible, and therefore, domain experts start exploration with the identification of correlations. The increased availability of data from open government websites, organizations, and scientific studies presents an opportunity to harness observational datasets in assisting domain experts during this exploratory phase.In this work, we introduce Nexus, a system designed to align large repositories of spatio-temporal datasets and identify correlations, facilitating the exploration of causal relationships. Nexus addresses the challenges of aligning tabular datasets across space and time, handling missing data, and identifying correlations deemed "interesting". Empirical evaluation on Chicago Open Data and United Nations datasets demonstrates the effectiveness of Nexus in exposing interesting correlations, many of which have undergone extensive scrutiny by social scientists.},
journal = {Proc. ACM Manag. Data},
month = may,
articleno = {154},
numpages = {28},
keywords = {correlation analysis, data discovery, hypothesis generation, spatio-temporal data}
}