How to get the sum of two elements in a list of arrays in Scala
Hi and thanks in advance for reading this time.
I am writing a piece of code in Scala to read a data file and create a couple of aggregations. For simplicity, let's assume the content looks like the following (entries are tab delimited):
01/12/2015 JACK M 21XYZ 56 200
01/14/2015 JOHN M 22ABS 34 145
I want to multiply the last two numbers and store them together with the second element (Name) and then run some statistics (min, max, top 10, etc.)
The steps I have taken so far:
1- Read the file
val dat = scala.io.Source.fromFile("abs.txt")
2- Put content in the list
val datList = try dat.getLines.toList finally dat.close
3- Split each string into an array of strings
val datArray = datList.map(_.split('\t'))
after these steps i have an Array of strings. I am stuck at this point. I don't know how I can calculate the multiplication of the last two elements of each array and store the results in a map and have the name as a key.
When I try something like
val res = datArray.map(x => x(4).toInt * x(5).toDouble)
it returns a Unit and I can't do anything about it.
I would appreciate it if you can shed some light.
I found something similar in the following link, however it is between two separate arrays which seem to be simpler.
Elementary sum of arrays in Scala
Thank,
Moe
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This, of course, does not "return One". res
- array of doublings. You forgot the name, but it's easy to fix:
val res = datArray.map(x => x(1) -> x(4).toInt * x(5).toDouble)
You now have a sequence of tuples, Seq[(String, Double)]
where the first element is the name and the second is the product you are using.
You can do all sorts of things with this list:
- Convert it to a map
name
→score
:res.toMap
(beware: if you have duplicate entries of the same name, will be saved only the last of each set) - Find the entry with the lowest score:
val (name, score) = res.minBy(_._2)
- Find the record with the highest score: `val (name, score) = res.maxBy (_._ 2)
- Find the total of all results:
res.map(_._2).sum
- Find ten records:
res.sortBy(-_._2).take(10)
- Combine the grades with the same name and make a map as in the first item, but with the values being the final grades for each name:
res.groupBy(_._1).mapValues(_.map(_._2).sum)
- etc.
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