I want to calculate the mean of every two consecutive elements in array a, and return a new array. The parameter type T can be any of the numerical type such as Byte, Short, Int, Float, and Double. I don't know how to make it work. Thanks in advance!
def center[T](a: Array[T]): Array[T] = {
for (i <- 0 until a.size - 1) yield (a(i) + a(i + 1)) / 2
}
One issue we have to deal with is that integer division produces an integer result: (2+3)/2 == 2
If we decide that we always want fractional results (maybe Double?) then it simplifies the task a bit. What's left is how to deal with input of any number type.
def center[N](a:Array[N])(implicit ev:Numeric[N]):Array[Double] = {
import ev._
if (a.lengthIs < 2) a.map(_.toDouble)
else a.sliding(2)
.map{case Array(a,b) => (a+b).toDouble/2.0}.toArray
}
testing:
center(Array(2, 3, 11, 4, 71))
//res0: Array[Double] = Array(2.5, 7.0, 7.5, 37.5)
center(Array(2.3, 1.1, 4.5, 7.1))
//res1: Array[Double] = Array(1.7, 2.8, 5.8)
Array[T] is only difficult if A) you want T to handle both fractional and integral numbers, and B) division is required. Integral division is a different operation than fractional division. See this rather old question for more details on the subject.This code example without dividing because of you should define your own typeclass for diving by integer value.
def center[T: Numeric](a: Array[T]): Array[T] = {
a.sliding(2).map { case Array(f, s) => Numeric[T].plus(f, s) }.toArray
}
[T: Numeric]