Number of Cycles from list of values, which are mix of positives and negatives in Spark and Scala - scala

Question

Have an RDD with List of values, which are mix of positives and negatives.
Need to compute number of cycles from this data.
For example,
val range = List(sampleRange(2020,2030,2040,2050,-1000,-1010,-1020,Starting point,-1030,2040,-1020,2050,2040,2020,end point,-1060,-1030,-1010)
the interval between each value in above list is 1 second. ie., 2020 and 2030 are recorded in 1 second interval and so on.
how many times it turns from negative to positive and stays positive for >= 2 seconds.
If >= 2 seconds it is a cycle.
Number of cycles: Logic
Example 1: List(1,2,3,4,5,6,-15,-66)
No. of cycles is 1.
Reason: As we move from 1st element of list to 6th element, we had 5 intervals which means 5 seconds. So one cycle.
As we move to 6th element of list, it is a negative value. So we start counting from 6th element and move to 7th element. The negative values are only 2 and interval is only 1. So not counted as cycle.
Example 2:
List(11,22,33,-25,-36,-43,20,25,28)
No. of cycles is 3.
Reason: As we move from 1st element of list to 3rd element, we had 2 intervals which means 2 seconds. So one cycle As we move to 4th element of list, it is a negative value. So we start counting from 4th element and move to 5th, 6th element. we had 2 intervals which means 2 seconds. So one cycle As we move to 7th element of list, it is a positive value. So we start counting from 7th element and move to 8th, 9th element. we had 2 intervals which means 2 seconds. So one cycle.
range is a RDD in the use case. It looks like
scala> range
range: Seq[com.Range] = List(XtreamRange(858,890,899,920,StartEngage,-758,-790,-890,-720,920,940,950))

Answer 1

You can encode this "how many times it turns from negative to positive and stays positive for >= 2 seconds. If >= 2 seconds it is a cycle." pretty much directly into a pattern match with a guard. The expression if(h < 0 && ht > 0 && hht > 0) checks for a cycle and adds one to the result then continues with the rest of the list.
def countCycles(xs: List[Int]): Int = xs match {
case Nil => 0
case h::ht::hht::t if(h < 0 && ht > 0 && hht > 0) => 1 + countCycles(t)
case h::t => countCycles(t)
}
scala> countCycles(range)
res7: Int = 1

Answer 2

A one liner
range.sliding(3).count{case f::s::t::Nil => f < 0 && s > 0 && t > 0}
This generates all sub-sequences of length 3 and counts how many are -ve, +ve, +ve
Generalising cycle length
def countCycles(n:Int, xs:List[Int]) = xs.sliding(n+1)
.count(ys => ys.head < 0 && ys.tail.forall(_ > 0))

Answer 3

The below code would help you resolve you query.
object CycleCheck {
def main(args: Array[String]) {
var data3 = List(1, 4, 82, -2, -12, "startingpoint", -9, 32, 76,45, -98, 76, "Endpoint", -24)
var data2 = data3.map(x => getInteger(x)).filter(_ != "unknown").map(_.toString.toInt)
println(data2)
var nCycle = findNCycle(data2)
println(nCycle)
}
def getInteger(obj: Any) = obj match {
case n: Int => obj
case _ => "unknown"
}
def findNCycle(obj: List[Int]) : Int = {
var cycleCount =0
var sign = ""
var signCheck="+"
var size = obj.size - 1
var numberOfCycles=0
var i=0
for( x <- obj){
if (x < 0){
sign="-"
}
else if (x > 0){
sign="+"
}
if(signCheck.equals(sign))
cycleCount=cycleCount+1
if(!signCheck.equals(sign) && cycleCount>1){
cycleCount = 1
numberOfCycles=numberOfCycles+1
}
if(size==i && cycleCount>1)
numberOfCycles= numberOfCycles+1
if(cycleCount==1)
signCheck = sign;
i=i+1
}
return numberOfCycles
}
}