Home
Insert
Update snippet 'Chronological sequence window beginnings'
Title
Description
An abstraction of the following use case: Given a sequence of dates and max temperatures for each date, extract out the initial dates on which the temp is greater than a given threshold for n consecutive days. (Originally posted as an answer to this StackOverflow question: http://stackoverflow.com/questions/5267055 )
Source code
let findWindowBeginnings predicate minWindowSize data = if minWindowSize < 2 then invalidArg "minWindowSize" "minWindowSize must be greater than 1" ((None, []), data) ||> Seq.fold (fun (window, acc) x -> if predicate x then match window with | Some (start, size) -> let size' = size + 1 let acc' = if size' = minWindowSize then start::acc else acc Some (start, size'), acc' | _ -> Some (x, 1), acc else None, acc) |> snd |> List.rev // example usage, implementing described use case: let findHeatwaveBeginnings tempThreshold consecutiveDays data = (consecutiveDays, data) ||> findWindowBeginnings (snd >> (<) tempThreshold) // alternatively, if one isn't a fan of point-free style code: // findWindowBeginnings (fun (_, maxTemp) -> maxTemp > tempThreshold) |> List.map fst
Tags
sequence
window
fold
sequence
window
fold
Author
Link
Reference NuGet packages
If your snippet has external dependencies, enter the names of NuGet packages to reference, separated by a comma (
#r
directives are not required).
Update
