0 people like it.

# Take a sample of a sequence

Take a sample of a specified length from a sequence. The sample is guaranteed to be of the requested size (unless there are too few elements in the original sequence). Sample items will be taken at equal intervals. (This version with some simplifications and tidy-ups.)

 ``` 1: 2: 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: 13: 14: 15: 16: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: 31: 32: 33: 34: 35: 36: 37: 38: 39: 40: 41: 42: 43: 44: 45: ``` ``````open System module Seq = // As Seq.filter but provide i as a parameter to the filter function. let filteri f s = s |> Seq.mapi (fun i elem -> i, elem) |> Seq.filter (fun (i, elem) -> f i elem) |> Seq.map (fun (_, elem) -> elem) module Sample = let sample size seq = // Get sample length: let len = seq |> Seq.length // Handle request for sample from empty sequence: if size = 0 then Seq.empty else // Approximate an interval between samples: let interval = Math.Max(len / size, 1) // Get the sample, truncating in case rounding meant too many elements: seq |> Seq.filteri (fun i _ -> i % interval = 0) |> Seq.truncate size open Sample let eleven = [1..11] // seq [1] let test1 = eleven |> sample 1 // seq [1; 7] let test2 = eleven |> sample 2 // seq [1; 5; 9] let test3 = eleven |> sample 3 // seq [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11] let test11 = eleven |> sample 11 // seq [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11] let test12 = eleven |> sample 12 ``````
namespace System
module Seq

from Microsoft.FSharp.Collections
val filteri : f:(int -> 'a -> bool) -> s:seq<'a> -> seq<'a>

Full name: Script.Seq.filteri
val f : (int -> 'a -> bool)
val s : seq<'a>
val mapi : mapping:(int -> 'T -> 'U) -> source:seq<'T> -> seq<'U>

Full name: Microsoft.FSharp.Collections.Seq.mapi
val i : int
val elem : 'a
val filter : predicate:('T -> bool) -> source:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.filter
val map : mapping:('T -> 'U) -> source:seq<'T> -> seq<'U>

Full name: Microsoft.FSharp.Collections.Seq.map
val sample : size:int -> seq:seq<'a> -> seq<'a>

Full name: Script.Sample.sample
val size : int
Multiple items
val seq : seq<'a>

--------------------
type seq<'T> = Collections.Generic.IEnumerable<'T>

Full name: Microsoft.FSharp.Collections.seq<_>
val len : int
Multiple items
module Seq

from Script

--------------------
module Seq

from Microsoft.FSharp.Collections
val length : source:seq<'T> -> int

Full name: Microsoft.FSharp.Collections.Seq.length
val empty<'T> : seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.empty
val interval : int
type Math =
static val PI : float
static val E : float
static member Abs : value:sbyte -> sbyte + 6 overloads
static member Acos : d:float -> float
static member Asin : d:float -> float
static member Atan : d:float -> float
static member Atan2 : y:float * x:float -> float
static member BigMul : a:int * b:int -> int64
static member Ceiling : d:decimal -> decimal + 1 overload
static member Cos : d:float -> float
...

Full name: System.Math
Math.Max(val1: decimal, val2: decimal) : decimal
Math.Max(val1: float, val2: float) : float
Math.Max(val1: float32, val2: float32) : float32
Math.Max(val1: uint64, val2: uint64) : uint64
Math.Max(val1: int64, val2: int64) : int64
Math.Max(val1: uint32, val2: uint32) : uint32
Math.Max(val1: int, val2: int) : int
Math.Max(val1: uint16, val2: uint16) : uint16
Math.Max(val1: int16, val2: int16) : int16
Math.Max(val1: byte, val2: byte) : byte
val truncate : count:int -> source:seq<'T> -> seq<'T>

Full name: Microsoft.FSharp.Collections.Seq.truncate
module Sample

from Script
val eleven : int list

Full name: Script.eleven
val test1 : seq<int>

Full name: Script.test1
val test2 : seq<int>

Full name: Script.test2
val test3 : seq<int>

Full name: Script.test3
val test11 : seq<int>

Full name: Script.test11
val test12 : seq<int>

Full name: Script.test12