根据值将数据集分组为不同的子数据集

Question

我想在由如下几列组成的数据集上实现一个程序：

+-----------+---------------+-------------------+-----------------------+
|Item_ID    |Product_Name   |Manufacturer_Name  |Product_Description    |
+-----------+---------------+-------------------+-----------------------+
|12345      |Pen            |Cello              |Ball Pen Soft Nib...   |
|12346      |Pencil         |Nataraja           |Pencil HB Extra D...   |
|42345      |Ruler          |Nataraja           |Scale No.1103 15c...   |
|12677      |Sharpener      |Nataraja           |Pencil Shraperner...   |
|12987      |Pen            |Reynolds           |Dot Pen Extra Gr...    |
|44326      |Pen            |Reynolds           |Gel Pen German T...    |
|13456      |Pen            |Cello              |Dot Pen 0.5mm Nib...   |
|19876      |Eraser         |Cello              |Dust free Eraser ...   |
|43246      |Ink Pen        |Hero               |Ink Pen Smooth Ha...   |
+-----------+---------------+-------------------+-----------------------+

我想根据Manufacturer_Name 对数据集进行分组，如下所示

Manufacturer = Cello
+-----------+---------------+-------------------+-----------------------+
|Item_ID    |Product_Name   |Manufacturer_Name  |Product_Description    |
+-----------+---------------+-------------------+-----------------------+
|12345      |Pen            |Cello              |Ball Pen Soft Nib...   |
|13456      |Pen            |Cello              |Dot Pen 0.5mm Nib...   |
|19876      |Eraser         |Cello              |Dust free Eraser ...   |
+-----------+---------------+-------------------+-----------------------+

Manufacturer = Nataraja
+-----------+---------------+-------------------+-----------------------+
|Item_ID    |Product_Name   |Manufacturer_Name  |Product_Description    |
+-----------+---------------+-------------------+-----------------------+
|12346      |Pencil         |Nataraja           |Pencil HB Extra D...   |
|42345      |Ruler          |Nataraja           |Scale No.1103 15c...   |
|12677      |Sharpener      |Nataraja           |Pencil Shraperner...   |
+-----------+---------------+-------------------+-----------------------+

Manufacturer = Reynolds
+-----------+---------------+-------------------+-----------------------+
|Item_ID    |Product_Name   |Manufacturer_Name  |Product_Description    |
+-----------+---------------+-------------------+-----------------------+
|12987      |Pen            |Reynolds           |Dot Pen Extra Gr...    |
|44326      |Pen            |Reynolds           |Gel Pen German T...    |
+-----------+---------------+-------------------+-----------------------+

Manufacturer = Hero
+-----------+---------------+-------------------+-----------------------+
|Item_ID    |Product_Name   |Manufacturer_Name  |Product_Description    |
+-----------+---------------+-------------------+-----------------------+
|43246      |Ink Pen        |Hero               |Ink Pen Smooth Ha...   |
+-----------+---------------+-------------------+-----------------------+

我尝试使用以下代码，但效果不佳。帮助我改进这个程序。这是我使用的代码：

Dataset<Row> countsBy = src.select("Manufacturer_Name").distinct();
List<Row> lsts = countsBy.collectAsList();
for (Row lst : lsts) {
    String man = lst.toString();
    System.out.println("Records of " + man + " only");
    Dataset<Row> mandataset = src.filter("Manufacturer_Name='" + man + "'");
    mandataset.show();
}

Answer 1

也许您可以尝试制作数据集的映射，键为字符串（Manufacturer_Name），对于每次迭代，您检查Manufacturer_Name，然后检查它是否已经在映射中（如果需要，您可以创建它）和最后，将行添加到好的数据集中。

你会有类似的东西：

Map<string,ArrayList<ShopItem>> dic = new HashMap<string,ArrayList<ShopItem>>();
for(/*...*/)
{
  string Manufacturer_Name = //you get the name
  if(/*the Manufacturer_Name is not in dic*/)
  {
    dic.put(Manufacturer_Name,new ArrayList<ShopItem>());
  }
  dic.get(Manufacturer_Name).Add(/*what you want to add*/);
}

然后您需要第二个循环，但仅用于打印数据。

希望能解决你的问题！

编辑：用地图替换字典（对不起）并提供链接

How do you create a dictionary in Java?

编辑：更改代码以匹配新想法