> For the complete documentation index, see [llms.txt](https://upsolver.gitbook.io/content/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://upsolver.gitbook.io/content/reference-1/functions-and-operators/functions/filter.md). # Filter This section describes the following filter functions:

Function	Description
IS_DUPLICATE	Returns true if it is not the first time a job sees the input value in the data within the specified window size (measured in minutes)
NOT	Returns true if the input is false, false if the input is true, null if the input is null, and applies this same logic to each element of an array input

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