lawblog-mapmonoid.scala

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))

scala> val dataset2 = Map("modelA" -> Evaluation(5,4))
dataset2: scala.collection.immutable.Map[String,Evaluation] = 
    Map(modelA -> Evaluation(5,4))

scala> mm.append(dataset1,dataset2)
res3: Map[String,Evaluation] = 
    Map(modelA -> Evaluation(8,6), modelB -> Evaluation(4,1))