> For the complete documentation index, see [llms.txt](https://george-jen.gitbook.io/data-science-and-apache-spark/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://george-jen.gitbook.io/data-science-and-apache-spark/map-func.md).

# map(func)

### map(func)

Return a new DStream by passing each element of the source DStream through a function func.

```
    val wordCounts = words.map(x => (x, 1)).reduceByKey(_ + _)

```

### flatMap(func)

Similar to map, but each input item can be mapped to 0 or more output items.  

```
//split words from line separated by space, such as sentence
    val lines = ssc.socketTextStream("localhost", 29999
      , StorageLevel.MEMORY_AND_DISK_SER)
    val words = lines.flatMap(_.split(" "))

```

There are choises of StorageLevel:

```
DISK_ONLY = StorageLevel(True, False, False, False, 1)
DISK_ONLY_2 = StorageLevel(True, False, False, False, 2)
MEMORY_AND_DISK = StorageLevel(True, True, False, False, 1)
MEMORY_AND_DISK_2 = StorageLevel(True, True, False, False, 2)
MEMORY_AND_DISK_SER = StorageLevel(True, True, False, False, 1)
MEMORY_AND_DISK_SER_2 = StorageLevel(True, True, False, False, 2)
MEMORY_ONLY = StorageLevel(False, True, False, False, 1)
MEMORY_ONLY_2 = StorageLevel(False, True, False, False, 2)
MEMORY_ONLY_SER = StorageLevel(False, True, False, False, 1)
MEMORY_ONLY_SER_2 = StorageLevel(False, True, False, False, 2)
OFF_HEAP = StorageLevel(True, True, True, False, 1)
(2 means RDD partitions will have replication of 2)
```