Matrices with Kotlin (using kotlin-statistics)

matrices_demo.kt

    import java.time.LocalDate
    import java.time.temporal.ChronoUnit
    import org.apache.commons.math3.linear.Array2DRowRealMatrix
    import org.apache.commons.math3.linear.RealMatrix

    fun main(args: Array<String>) {

       val matrix = patients.toMatrix(
               { it.age },
               { it.whiteBloodCellCount },
               { if (it.gender == Gender.MALE) 0 else 1 }
       )

       println(matrix.toFormattedString())
    }

    data class Patient(val firstName: String,
                       val lastName: String,
                       val gender: Gender,
                       val birthday: LocalDate,
                       val whiteBloodCellCount: Int)  {

        val age = ChronoUnit.YEARS.between(birthday, LocalDate.now())
    }

    val patients = listOf(
            Patient("John", "Simone", Gender.MALE, LocalDate.of(1989, 1, 7), 4500),
            Patient("Sarah", "Marley", Gender.FEMALE, LocalDate.of(1970, 2, 5), 6700),
            Patient("Jessica", "Arnold", Gender.FEMALE, LocalDate.of(1980, 3, 9), 3400),
            Patient("Sam", "Beasley", Gender.MALE, LocalDate.of(1981, 4, 17), 8800),
            Patient("Dan", "Forney", Gender.MALE, LocalDate.of(1985, 9, 13), 5400),
            Patient("Lauren", "Michaels", Gender.FEMALE, LocalDate.of(1975, 8, 21), 5000),
            Patient("Michael", "Erlich", Gender.MALE, LocalDate.of(1985, 12, 17), 4100),
            Patient("Jason", "Miles", Gender.MALE, LocalDate.of(1991, 11, 1), 3900),
            Patient("Rebekah", "Earley", Gender.FEMALE, LocalDate.of(1985, 2, 18), 4600),
            Patient("James", "Larson", Gender.MALE, LocalDate.of(1974, 4, 10), 5100),
            Patient("Dan", "Ulrech", Gender.MALE, LocalDate.of(1991, 7, 11), 6000),
            Patient("Heather", "Eisner", Gender.FEMALE, LocalDate.of(1994, 3, 6), 6000),
            Patient("Jasper", "Martin", Gender.MALE, LocalDate.of(1971, 7, 1), 6000)
    )

    enum class Gender {
        MALE,
        FEMALE
    }


class Matrix(private val m: RealMatrix) {


    operator fun get(row: Int, col: Int) = m.getEntry(row, col)
    operator fun get(row: Int) = m.getRow(row)

    fun transpose() = m.transpose().let(::Matrix)

    val data get() = m.data

    fun toFormattedString() = data.asSequence().map { it.joinToString(" ")}.joinToString("\r\n")

}

fun <T> Iterable<T>.toMatrix(vararg fieldMappers: (T) -> Number) =
        toList().let {
            val colCount = fieldMappers.size
            val rowCount = it.size

            val m = Array2DRowRealMatrix(rowCount, colCount)

            it.forEachIndexed { rowIndex, item ->
               fieldMappers.forEachIndexed { colIndex, mapper ->
                   m.setEntry(rowIndex, colIndex,mapper(item).toDouble())
               }
            }

            Matrix(m)
        }