Flatten array in yield statement in Scala - scala

Question

I have the following piece of code
var splitDf = fullCertificateSourceDf.map(row => {
val ID = row.getAs[String]("ID")
val CertificateID = row.getAs[String]("CertificateID")
val CertificateTag = row.getAs[String]("CertificateTag")
val CertificateDescription = row.getAs[String]("CertificateDescription")
val WorkBreakdownUp1Summary = row.getAs[String]("WorkBreakdownUp1Summary")
val ProcessBreakdownSummaryList = row.getAs[String]("ProcessBreakdownSummaryList")
val ProcessBreakdownUp1SummaryList = row.getAs[String]("ProcessBreakdownUp1SummaryList")
val ProcessBreakdownUp2Summary = row.getAs[String]("ProcessBreakdownUp2Summary")
val ProcessBreakdownUp3Summary = row.getAs[String]("ProcessBreakdownUp3Summary")
val ActualStartDate = row.getAs[java.sql.Date]("ActualStartDate")
val ActualEndDate = row.getAs[java.sql.Date]("ActualEndDate")
val ApprovedDate = row.getAs[java.sql.Date]("ApprovedDate")
val CurrentState = row.getAs[String]("CurrentState")
val DataType = row.getAs[String]("DataType")
val PullDate = row.getAs[String]("PullDate")
val PullTime = row.getAs[String]("PullTime")
val split_ProcessBreakdownSummaryList = ProcessBreakdownSummaryList.split(",")
val split_ProcessBreakdownUp1SummaryList = ProcessBreakdownUp1SummaryList.split(",")
val Pattern = "^.*?(?= - *[a-zA-Z])".r
for{
subSystem : String <- split_ProcessBreakdownSummaryList
} yield(ID,
CertificateID,
CertificateTag,
CertificateDescription,
WorkBreakdownUp1Summary,
subSystem,
for{ system: String <- split_ProcessBreakdownUp1SummaryList if(system contains subSystem.trim().substring(0,11))}yield(system),
ProcessBreakdownUp2Summary,
ProcessBreakdownUp3Summary,
ActualStartDate,
ActualEndDate,
ApprovedDate,
CurrentState,
DataType,
PullDate,
PullTime
)
}).flatMap(identity(_))
display(splitDf)
How can I get the first matching element from the following portion of the above statement:
for{ system: String <- split_ProcessBreakdownUp1SummaryList if(system contains subSystem.trim().substring(0,11))}yield(system)
At the moment it returns an array with one element in it. I dont want the array I just want the element.
Thank you in advance.