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Euler

Euler method is a first-order numerical procedure for solving ordinary differential equations (ODEs) with a given initial value.

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let euler f a b n y0 =
    let h = (b - a) / (float) n
    let rec euler f x y0 h =
        match x with
        | x0::x1::xt -> let y1 = y0 + f(x0,y0) * h
                        let yx = y0 + (f(x0,y0) + f(x1,y1)) / 2.0 * h
                        printfn "%.06f %.06f %.06f" x1 y1 yx
                        euler f ([x1]@xt) yx h
        | _ -> y0
    euler f [a..h..b] y0 h


//This is the function values
let k1 = 0.00002
let k2 = 0.0001
let m = 100000.0
let x0 = 99000.0
let f(x,y) = k2*(m-y-x0*exp(-k1/k2*y))

let a = 0.0
let b = 10.0
let n = 5 // (b - a) / 2.0
let y = 5213.95256

//Usage
euler f a b n y

val euler : f:(float * float -> float) -> a:float -> b:float -> n:int -> y0:float -> float

Full name: Script.euler

val f : (float * float -> float)

val a : float

val b : float

val n : int

val y0 : float

val h : float

Multiple items
val float : value:'T -> float (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.float

--------------------
type float = System.Double

Full name: Microsoft.FSharp.Core.float

--------------------
type float<'Measure> = float

Full name: Microsoft.FSharp.Core.float<_>

val euler : ((float * float -> float) -> float list -> float -> float -> float)

val x : float list

val x0 : float

val x1 : float

val xt : float list

val y1 : float

val yx : float

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

val k1 : float

Full name: Script.k1

val k2 : float

Full name: Script.k2

val m : float

Full name: Script.m

val x0 : float

Full name: Script.x0

val f : x:'a * y:float -> float

Full name: Script.f

val x : 'a

val y : float

val exp : value:'T -> 'T (requires member Exp)

Full name: Microsoft.FSharp.Core.Operators.exp

val a : float

Full name: Script.a

val b : float

Full name: Script.b

val n : int

Full name: Script.n

val y : float

Full name: Script.y

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More information

Link:	http://fssnip.net/7RU
Posted:	7 years ago
Author:	Ivan Padron
Tags:	math , mathematic