spark scala map转 rdd 然后转 dataframe的方法，主要用到seq的toDF方法

    var subjectScoreLevelDetail:Seq[Map[String,String]]=Seq(Map("subjectId"->"001","excellent"->"90","good"->"80","pass"->"60"),Map("subjectId"->"002","excellent"->"90","good"->"80","pass"->"60"))

    var s=subjectScoreLevelDetail.map(kv=>{(kv.get("subjectId"),kv.get("excellent").get.toDouble,kv.get("good").get.toDouble,kv.get("pass").get.toDouble)})

    var dataframe=s.toDF("subjectId","excellent","good","pass")
    dataframe.show