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High-performance Java Dataframe with integrated columnar storage (fork of tablesaw)

There is a newer version: 0.9.1

package org.datavec.dataframe.io.csv;

import org.datavec.dataframe.api.Table;
import org.datavec.dataframe.columns.Column;
import com.opencsv.CSVWriter;

import javax.annotation.concurrent.Immutable;
import java.io.FileWriter;
import java.io.IOException;

/**
 * Static utility class that writes tables and individual columns to CSV files
 * 
 * TODO(lwhite): Do something with the missing indicator param in write() method
 * TODO(lwhite): Add a missing indicator to the column write method, plus a method defining a default missing indicator
 */
@Immutable
final public class CsvWriter {

  /**
   * Private constructor to prevent instantiation
   */
  private CsvWriter() {
  }

  /**
   * Writes the given table to a file with the given filename
   *
   * @throws IOException
   */
  public static void write(String fileName, Table table) throws IOException {
    write(fileName, table, null);
  }

  /**
   * Writes the given table to a file with the given filename, using the given string to represent missing data
   *
   * @throws IOException
   */
  public static void write(String fileName, Table table, String missing) throws IOException {
    try (CSVWriter writer = new CSVWriter(new FileWriter(fileName))) {
      String[] header = new String[table.columnCount()];
      for (int c = 0; c < table.columnCount(); c++) {
        header[c] = table.column(c).name();
      }
      writer.writeNext(header);
      for (int r = 0; r < table.rowCount(); r++) {
        String[] entries = new String[table.columnCount()];
        for (int c = 0; c < table.columnCount(); c++) {
          table.get(c, r);
          entries[c] = table.get(c, r);
        }
        writer.writeNext(entries);
      }
    }
  }

  /**
   * Writes the given column to a file with the given fileName as a single column CSV file
   *
   * @throws IOException
   */
  public static void write(String fileName, Column column) throws IOException {
    try (CSVWriter writer = new CSVWriter(new FileWriter(fileName))) {
      String[] header = {column.name()};
      writer.writeNext(header);

      for (int r = 0; r < column.size(); r++) {
        String[] entries = {column.getString(r)};
        writer.writeNext(entries);
      }
    }
  }
}