The demo dataset (demo/prices.csv)

The file is a fixed snapshot of daily closes for GOOGL, MSFT and the S&P 500 index (SPX): 1435 trading days each, 2021-01-04 … 2026-09-21, one calendar shared by all three. It is a long table (date, symbol, price) committed on purpose, so the quick start can be copied and run as-is.

It ships twice, on purpose: in the repository as demo/prices.csv, and under docs/static/demo/ so the docs site serves it at https://shijianjs.github.io/duckfn-quantstats/demo/prices.csv — the URL every example in these pages reads, and the only one that works from a browser (DuckDB-Wasm cannot read a repository URL).

Why a snapshot and not a live URL. When this was written there was no free, key-less and stable HTTP endpoint for the daily closes of individual tickers: stooq puts a JavaScript challenge in front of its CSV download, Yahoo's endpoint answers with region redirects, and EODHD's public demo token dies on quota after a handful of requests. FRED does export the index as CSV (https://fred.stlouisfed.org/graph/fredgraph.csv?id=SP500), but it rejects the HEAD probe read_csv sends first, so that one cannot be read directly either.

The snapshot was therefore taken on 2026-09-22 — the index from that FRED CSV, the stocks from Nasdaq's public quote API (https://api.nasdaq.com/api/quote/MSFT/historical?assetclass=stocks&fromdate=2021-01-01&todate=2026-09-21&limit=2000), close prices as served.