Seq.windowed<'T> Function (F#)

Returns a sequence that yields sliding windows of containing elements drawn from the input sequence. Each window is returned as a fresh array.

Namespace/Module Path: Microsoft.FSharp.Collections.Seq

Assembly: FSharp.Core (in FSharp.Core.dll)

// Signature:
Seq.windowed : int -> seq<'T> -> seq<'T []>

// Usage:
Seq.windowed windowSize source

Parameters

• windowSize
  Type: int

  The number of elements in each window.

• source
  Type: seq<'T>

  The input sequence.

Exceptions

Exception	Condition
ArgumentException	Thrown when the input sequence is empty.
ArgumentNullException	Thrown when the input sequence is null.

Return Value

The result sequence.

Remarks

This function is named Windowed in compiled assemblies. If you are accessing the function from a language other than F#, or through reflection, use this name.

Example

The following example demonstrates the use of Seq.windowed as part of a computation of a moving average for a sequence of numbers.

let seqNumbers = [ 1.0; 1.5; 2.0; 1.5; 1.0; 1.5 ] :> seq<float>
let seqWindows = Seq.windowed 3 seqNumbers
let seqMovingAverage = Seq.map Array.average seqWindows
printfn "Initial sequence: "
printSeq seqNumbers
printfn "\nWindows of length 3: "
printSeq seqWindows
printfn "\nMoving average: "
printSeq seqMovingAverage

Initial sequence: 
1.0 1.5 2.0 1.5 1.0 1.5 

Windows of length 3: 
[|1.0; 1.5; 2.0|] [|1.5; 2.0; 1.5|] [|2.0; 1.5; 1.0|] [|1.5; 1.0; 1.5|] 

Moving average: 
1.5 1.666666667 1.5 1.333333333 

Platforms

Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2

Version Information

F# Runtime

Supported in: 2.0, 4.0

Silverlight

Supported in: 3

See Also

Reference

Collections.Seq Module (F#)

Microsoft.FSharp.Collections Namespace (F#)