David Andrzejewski davidandrzej

I hereby claim:

I am davidandrzej on github.
I am davidandrzej (https://keybase.io/davidandrzej) on keybase.
I have a public key whose fingerprint is 5203 3009 B157 505D DF21 9C16 B86B BB05 D29E 1BFE

To claim this, I am signing this object:

	function [l v] = grasshopper(W, r, lambda, k)
	%
	% Reranking items by random walk on graph with absorbing states.
	% (CREDIT: Jerry Zhu [email protected])
	%
	% INPUT
	%
	% W: n*n weight matrix with non-negative entries.
	% W(i,j) = edge weight for the edge i->j
	% The graph can be directed or undirected. Self-edges are allowed.

	scala> implicit val em = EvaluationMonoid
	em: EvaluationMonoid.type = EvaluationMonoid$@34f5b235

	scala> implicit val mm = mapMonoid[String,Evaluation]
	mm: scalaz.Monoid[Map[String,Evaluation]] = scalaz.std.MapInstances$$anon$4@13105b09

	scala> val dataset1 = Map("modelA" -> Evaluation(3,2),
	\| "modelB" -> Evaluation(4,1))
	dataset1: scala.collection.immutable.Map[String,Evaluation] =
	Map(modelA -> Evaluation(3,2), modelB -> Evaluation(4,1))

	val evalGen = for {total <- Gen.choose(0, 1000);
	correct <- Gen.choose(0, total)}
	yield Evaluation(total,correct)

	"Evaluation Monoid" should {

	import EvaluationMonoid._
	implicit val eq = Equal.equalA[Evaluation]

	"obey Monoid typeclass Law" in {

	"Evaluation Monoid" should {

	import EvaluationMonoid._
	implicit val eq = Equal.equalA[Evaluation]
	val testEvaluation = Evaluation(3, 2)

	"obey Monoid typeclass Law" in {
	Monoid.monoidLaw.leftIdentity(testEval) should be (true)
	Monoid.monoidLaw.rightIdentity(testEval) should be (true)
	}

	object EvaluationMonoid extends Monoid[Evaluation] {
	def zero = Evaluation(0,0)
	def append(x: Evaluation, y: => Evaluation) =
	Evaluation(x.total + y.total, x.correct + y.correct)
	}

	trait Monoid[F] extends Semigroup[F] {
	...
	trait MonoidLaw extends SemigroupLaw {
	def leftIdentity(a: F)(implicit F: Equal[F]) =
	F.equal(a, append(zero, a))
	def rightIdentity(a: F)(implicit F: Equal[F]) =
	F.equal(a, append(a, zero))
	}
	...
	}

	def addItUp[F : Monoid](items: Seq[F]): F = {
	// Combine a bunch of items
	val m = implicitly[Monoid[F]]
	items.foldLeft(m.zero){case (total, next) => m.append(total,next)}
	}

	scala> addItUp(Seq("day ", "after ", "day"))
	res1: String = "day after day"
	scala> addItUp(Seq(1,2,3))
	res2: Int = 6