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Course 2: Freebase, queries, linear regression

F# introduction course - Getting data about cyclones from Freebase and plotting the dependency of damages in USD on the wind speed (with linear regression). To be used in Try F#.

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// Load Freebase data connection and charting library
#r "Samples.DataStore.Freebase.dll"
open Samples.Charting.DojoChart
open Samples.DataStore.Freebase

let freebase = FreebaseData.GetDataContext()

// ------------------------------------------------------------------
// DEMO: Querying cyclone data using F# LINQ
// ------------------------------------------------------------------

let cyclones = 
  query { for x in freebase.Commons.Meteorology.``Tropical Cyclones`` do
          where x.``Highest winds``.HasValue
          where (x.Damages.Currency.Name = "United States dollar")
          select (x.``Highest winds``.Value, x.Damages.Amount.Value / 1e9) }
  |> Seq.toList

// Plot wind speed and damage in USD as point chart
let cyclonChart =    
  Chart.Point(cyclones) 
    .WithYAxis(Title="Damage (US$)")
    .WithXAxis("Wind Speed")

// ------------------------------------------------------------------
// DEMO: Adding linear regression using Math.NET
// ------------------------------------------------------------------

// For more information see
// http://christoph.ruegg.name/blog/linear-regression-mathnet-numerics.html

#r "MathNet.Numerics.dll"
open MathNet.Numerics.LinearAlgebra
open MathNet.Numerics.LinearAlgebra.Double

// Build matrix and vector representing the equation system 
let cols : Generic.Vector<float>[] = 
  [| DenseVector(cyclones.Length, 1.0)
     DenseVector([| for x, y in cyclones -> float x |]) |] 
let x = DenseMatrix.CreateFromColumns(cols)
let y = DenseVector([| for x, y in cyclones -> y |])

// QR decomposition gives us attributes of y=a+x*b line
let [| a; b |] = x.QR().Solve(y) |> Seq.toArray

// Draw chart with linear regression
Chart.Combine
  [ cyclonChart
    Chart.Line([20.0, a+b*20.0; 100.0, a+b*100.0 ]) ]
    
val freebase : obj

Full name: Script.freebase
val cyclones : (obj * float) list

Full name: Script.cyclones
val query : Linq.QueryBuilder

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.query
val x : obj
custom operation: where (bool)

Calls Linq.QueryBuilder.Where
custom operation: select ('Result)

Calls Linq.QueryBuilder.Select
module Seq

from Microsoft.FSharp.Collections
val toList : source:seq<'T> -> 'T list

Full name: Microsoft.FSharp.Collections.Seq.toList
val cyclonChart : obj

Full name: Script.cyclonChart
val cols : obj []

Full name: Script.cols
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<_>
property List.Length: int
val x : obj

Full name: Script.x
val y : obj

Full name: Script.y
val a : obj

Full name: Script.a
val b : obj

Full name: Script.b
val toArray : source:seq<'T> -> 'T []

Full name: Microsoft.FSharp.Collections.Seq.toArray
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More information

Link:http://fssnip.net/ja
Posted:3 years ago
Author:Tomas Petricek
Tags: freebase , type provider , try f#