Instance object that handles missing values.

instance_v02.scala

object Instance {
    def parseCSV( instanceAsCSVString: String): Instance = {
        def extractFeatureValues( parsedInstance: Array[ String]): List[ Option[Double]] = {
            val featuresStartIndex = 0
            val featuresEndIndex = parsedInstance.length - 2
            
            val featureBuffer = new ListBuffer[Option[Double]]()
            for ( index <- featuresStartIndex to featuresEndIndex) {
                val token = parsedInstance( index)
                val value = try {
                    Some( token.toDouble)
                } catch {
                    case nfe: NumberFormatException => {
                        if ( token == "?") {
                            None
                        } else {
                            throw new MalformedInstanceException
                        }
                    }
                }
                featureBuffer += value
            }
            featureBuffer.toList
        }
        val parsedInstance = instanceAsCSVString.split( ",")
        val featureValues = extractFeatureValues( parsedInstance)
        val classLabelIndex = parsedInstance.length - 1
        val classLabel = parsedInstance( classLabelIndex)
        new Instance( featureValues, Some( classLabel))
    }   
}