How to read csv file into an Array of arrays in scala

Question

I'm trying to read a csv file and return it as an array of arrays of doubles (Array[Array[Double]]). It's pretty clear how to read in a file line by line and immediately print it out, but not how to store it in a two-dimensional array.

def readCSV() : Array[Array[Double]] = {
    val bufferedSource = io.Source.fromFile("/testData.csv")
    var matrix :Array[Array[Double]] = null
    for (line <- bufferedSource.getLines) {
        val cols = line.split(",").map(_.trim)
        matrix = matrix :+ cols
    }
    bufferedSource.close
    return matrix
}

Had some type issues and then realized I'm not doing what I thought I was doing. Any help pointing me on the right track would be very appreciated.

Helder Pereira · Accepted Answer · 2015-08-17 17:16:44Z

6

It seems your question was already answered. So just as a side note, you could write your code in a more scalaish way like this:

def readCSV() : Array[Array[Double]] = {
  io.Source.fromFile("/testData.csv")
    .getLines()
    .map(_.split(",").map(_.trim.toDouble))
    .toArray
}

answered Aug 17, 2015 at 17:16

Helder Pereira

5,7713 gold badges39 silver badges55 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sascha Kolberg · Accepted Answer · 2015-08-17 17:00:55Z

1

1) You should start with an empty Array unstead of null. 2) You append items to an Array with the operator :+ 3) As your result type is Array[Array[Double]] you need to convert the strings of the csv to Double.

def readCSV() : Array[Array[Double]] = {
    val bufferedSource = io.Source.fromFile("/testData.csv")
    var matrix :Array[Array[Double]] = Array.empty
    for (line <- bufferedSource.getLines) {
        val cols = line.split(",").map(_.trim.toDouble)
        matrix = matrix :+ cols
    }
    bufferedSource.close
    return matrix
}

answered Aug 17, 2015 at 17:00

Sascha Kolberg

7,1721 gold badge34 silver badges37 bronze badges

1 Comment

user3413468 Over a year ago

Thank you! Turns out this gets you the array of rows, not the array of columns, but it doesn't take much to turn that into the columns.

Collectives™ on Stack Overflow

How to read csv file into an Array of arrays in scala

2 Answers 2

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related