Scala - Converting List[((String, String), Double)] to List[String,Map[String,Double]]

Question

I've got a list of data that is of the structure List[((String, Double), Double)] where the columns are Car Brand, Car ID and Average price. I want to reformat this data into List[String, Map[Int, Double]]. I'm unsure where to begin.

I suspect that I'm supposed to use something like .map(car => (car.brand, car.carColor, car.purchasePrice) to split the values out, then another map to put them into the structure that I require.

The code to generate the data that I wish to reformat is as follows

val carStats = cars.groupBy(c => (c.brand,
     c.carID)).mapValues(cars => car.map(_.purchasePrice).sum / cars.length).toList

I ultimately want this list to be reformatted into List[String, Map[String, Double]], but efforts so far haven't had much luck.

Can you share some example input and expected output? I believe you will have many Car Brand and many Car ID for each brand, and you want to group by both and compute the average price for each Card brand + Car ID. Also, can you please tell us which Scala version this has to be done. Finally, why List[(String, Map[String, Double]]? Wouldn't it be better a Map[String, Map[String, Double]]? — Luis Miguel Mejía Suárez
– Luis Miguel Mejía Suárez, Commented Oct 2, 2019 at 16:40

b1n0ys · Accepted Answer · 2019-10-02 18:29:02Z

2

is this what you are looking for ?

val result = carStats.map{case ((brand, id), avg_price) => (brand, id, avg_price)}.groupBy(_._1).mapValues(v => v.map{e => (e._2,e._3)}.toMap).toList

answered Oct 2, 2019 at 18:29

b1n0ys

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1 Comment

sheff1892 Over a year ago

That's exactly it, thanks very much. I was struggling to get my head around this.

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