%dw 2.0

var numbers = [10, 20, 30, 40, 50]

var words = ["MuleSoft", "DataWeave", "Delight"]

var books = [
    {
        title: "Lord of the rings",
        price: 30.0
    },
    {
        title: "Hitch-hiker's guide to the galaxy",
        price: 42.0
    }
]

output application/json
---
{
    // Average for a array of numbers.
    average: avg(numbers),

    // We can map our source objects to number values
    // and calculate the average.
    averageWordSize: avg(words map sizeOf($)),

    // The array of book object can be turned into
    // an array with only the prices and we can
    // calculate the average.
    averageBookPrice: avg(books map $.price)
}

{
  "average": 30,
  "averageWordSize": 8,
  "averageBookPrice": 36.0
}