> For the complete documentation index, see [llms.txt](https://sandyzeng.gitbook.io/kql/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sandyzeng.gitbook.io/kql/kql-quick-guide/need-to-learn-later/time-series/series_fir.md).

# series\_fir