add desc for clustering coefficient algorithm (#22)

* add desc for clustering coefficient algorithm

* update grammer

Author: Nicole00

README-CN.md

@@ -16,6 +16,7 @@ nebula-algorithm 是一款基于 [GraphX](https://spark.apache.org/graphx/) 的
  |     GraphTriangleCount   |全图三角形计数|网络紧密性分析|
  |   BetweennessCentrality  | 介数中心性  |关键节点挖掘，节点影响力计算|
  |        DegreeStatic      |   度统计   |图结构分析|
+ |   ClusteringCoefficient  |  聚集系数  |推荐，电信诈骗分析|
 
 使用 `nebula-algorithm`，可以通过提交 `Spark` 任务的形式使用完整的算法工具对 `Nebula Graph` 数据库中的数据执行图计算，也可以通过编程形式调用`lib`库下的算法针对DataFrame执行图计算。
 
@@ -32,8 +33,6 @@ nebula-algorithm 是一款基于 [GraphX](https://spark.apache.org/graphx/) 的
    https://repo1.maven.org/maven2/com/vesoft/nebula-algorithm/2.0.0/
 
 # 使用 Nebula Algorithm
-
-   使用限制：Nebula Algorithm 未自动对字符串id进行编码，因此执行图算法时，边的源点和目标点必须是整数（Nebula Space 的 vid_type可以是String类型，但数据必须是整数）。
    
 * 使用方法1：直接提交 nebula-algorithm 算法包
 
@@ -46,9 +45,12 @@ nebula-algorithm 是一款基于 [GraphX](https://spark.apache.org/graphx/) 的
     ```
     ${SPARK_HOME}/bin/spark-submit --master <mode> --class com.vesoft.nebula.algorithm.Main nebula-algorithm-2.0.0.jar -p application.conf
     ```
+    * 使用限制
+    
+    Nebula Algorithm 算法包未自动对字符串 id 进行编码，因此采用第一种方式执行图算法时，边的源点和目标点必须是整数（Nebula Space 的 vid_type 可以是 String 类型，但数据必须是整数）。
 * 使用方法2：调用 nebula-algorithm 算法接口
 
-   在`nebula-algorithm`的`lib`库中提供了10中常用图计算算法，可通过编程调用的形式调用算法。
+   在 `nebula-algorithm` 的 `lib` 库中提供了10中常用图计算算法，可通过编程调用的形式调用算法。
    * 在pom.xml中添加依赖
    ```
     <dependency>
@@ -67,18 +69,20 @@ nebula-algorithm 是一款基于 [GraphX](https://spark.apache.org/graphx/) 的
    val prConfig = new PRConfig(5, 1.0)
    val prResult = PageRankAlgo.apply(spark, data, prConfig, false)
    ```
- 
+   * 如果你的节点 id 是 String 类型，可以参考 PageRank 的 [Example](https://github.com/vesoft-inc/nebula-algorithm/blob/master/example/src/main/scala/com/vesoft/nebula/algorithm/PageRankExample.scala) 。 
+   该 Example 进行了 id 转换，将 String 类型 id 编码为 Long 类型的 id ， 并在算法结果中将 Long 类型 id 解码为原始的 String 类型 id 。
+   
     其他算法的调用方法见[测试示例](https://github.com/vesoft-inc/nebula-algorithm/tree/master/nebula-algorithm/src/test/scala/com/vesoft/nebula/algorithm/lib) 。
     
-    > 注：执行算法的DataFrame默认第一列是源点，第二列是目标点，第三列是边权重。
+    > 注：执行算法的 DataFrame 默认第一列是源点，第二列是目标点，第三列是边权重。
 
 ## 版本匹配
 
 | Nebula Algorithm Version | Nebula Version |
 |:------------------------:|:--------------:|
 |       2.0.0              |  2.0.0, 2.0.1  |
 |       2.1.0              |  2.0.0, 2.0.1  |
-|       2.5.0              |     2.5.0      |
+|       2.5.0              |     >=2.5.0    |
 |       2.5-SNAPSHOT       |     nightly    |
 
 ## 贡献

README.md

@@ -20,6 +20,7 @@ nebula-algorithm is a Spark Application based on [GraphX](https://spark.apache.o
 |    GraphTriangleCount    | network structure and tightness analysis|
 |   BetweennessCentrality  | important node digging, node influence calculation|
 |        DegreeStatic      | graph structure analysis|
+|   ClusteringCoefficient  | recommended, telecom fraud analysis|
 
 
 You could submit the entire spark application or invoke algorithms in `lib` library to apply graph algorithms for DataFrame.
@@ -41,8 +42,6 @@ You could submit the entire spark application or invoke algorithms in `lib` libr
 
 ## Use Nebula Algorithm
 
-Limitation: Due to Nebula Algorithm will not encode string id, thus during the algorithm execution, the source and target of edges must be in Type Int (The `vid_type` in Nebula Space could be String, while data must be in Type Int).
-
 * Option 1: Submit nebula-algorithm package
 
    * Configuration
@@ -55,6 +54,10 @@ Limitation: Due to Nebula Algorithm will not encode string id, thus during the a
     ${SPARK_HOME}/bin/spark-submit --master <mode> --class com.vesoft.nebula.algorithm.Main nebula-algorithm-2.0.0.jar -p application.conf
     ```
    
+   * Limitation
+    
+    Due to Nebula Algorithm jar does not encode string id, thus during the algorithm execution, the source and target of edges must be in Type Int (The `vid_type` in Nebula Space could be String, while data must be in Type Int).
+
 * Option2: Call nebula-algorithm interface
 
    Now there are 10 algorithms provided in `lib` from `nebula-algorithm`, which could be invoked in a programming fashion as below:
@@ -78,8 +81,9 @@ Limitation: Due to Nebula Algorithm will not encode string id, thus during the a
    val prResult = PageRankAlgo.apply(spark, data, prConfig, false)
    ```
    
-    For other algorithms, please refer to [test cases](https://github.com/vesoft-inc/nebula-algorithm/tree/master/nebula-algorithm/src/test/scala/com/vesoft/nebula/algorithm/lib).
-   
+   If your vertex ids are Strings, see [Pagerank Example](https://github.com/vesoft-inc/nebula-algorithm/blob/master/example/src/main/scala/com/vesoft/nebula/algorithm/PageRankExample.scala) for how to encoding and decoding them.
+    
+    For examples of other algorithms, see [examples](https://github.com/vesoft-inc/nebula-algorithm/tree/master/example/src/main/scala/com/vesoft/nebula/algorithm)
    > Note: The first column of DataFrame in the application represents the source vertices, the second represents the target vertices and the third represents edges' weight.
 
 ## Version match
@@ -88,7 +92,7 @@ Limitation: Due to Nebula Algorithm will not encode string id, thus during the a
 |:------------------------:|:--------------:|
 |       2.0.0              |  2.0.0, 2.0.1  |
 |       2.1.0              |  2.0.0, 2.0.1  |
-|       2.5.0              |     2.5.0      |
+|       2.5.0              |     >=2.5.0    |
 |       2.5-SNAPSHOT       |     nightly    |
 
 ## Contribute