Example of dense and uncommented code.

Submatrix.scala

/**
    * Creates a new matrix without specified rows & columns.
    *
    * @param deletedRows    rows to exclude from submatrix.
    * @param deletedColumns columns to exclude from submatrix.
    * @return defined submatrix.
    */
  def submatrix(deletedRows: Array[Int], deletedColumns: Array[Int]): MatrixF = {
    val result = Array.ofDim[Float](rowCount - deletedRows.count(rowCount >= _), columnCount - deletedColumns.count(columnCount >= _))
    data.indices.filterNot(deletedRows contains _ + 1).zipWithIndex.foreach { case (row, i) =>
      data(0).indices.filterNot(deletedColumns contains _ + 1).zipWithIndex.foreach { case (col, j) =>
        result(i)(j) = data(row)(col)
      }
    }
    new MatrixF(result)
  }