Cypher: How to Determine Degree Centrality and Rank Nodes by Influence Using Cypher Queries
Tags: apacheage, postgres, sql
Published: 2023-04-27 23:30:26

## Introduction

**Network analysis** has become an increasingly important tool in understanding complex systems in various fields, such as social sciences, biology, and computer science. One key aspect of network analysis is identifying the most important nodes in a network based on their centrality and influence. In this context, degree centrality is a widely used measure that quantifies the importance of a node based on its degree, or the number of connections it has to other nodes. However, once the degree centrality of nodes is determined, it is often useful to rank them by their influence in the network. In this article, we will explore how to use Cypher queries, a query language for graph databases, to determine the degree centrality of nodes in a network and rank them by influence. By the end of this article, readers will have a better understanding of how to use Cypher queries to extract valuable insights from network data.

## Motivation

Based on this [stack overflow question](https://stackoverflow.com/questions/76123775/is-there-a-way-to-determine-degree-centrality-of-an-apache-age-graph), I have been thinking of ways to perform sorting using Apache Age. How to determine the degree centrality of nodes in a graph using Cypher using APACHE AGE?

## Solution
The query is designed to analyze a graph that represents the relationships between people, where nodes represent people and edges represent friendships. The query uses the MATCH statement to find all nodes that have a "friend" relationship with another node, and then calculates the number of friends each person has. The query then orders the results by the number of friends in descending order, showing the most connected individuals at the top of the list. Finally, the query returns the names of each person along with their respective number of friends, using the "RETURN" statement. By using this query, we can gain insights into the most influential individuals in a social network, and potentially use this information for targeted marketing or social interventions.

```sql
SELECT * FROM cypher('graph', $$
    MATCH (v:people)-[r:friend]-(w:people)
    WITH v.name AS name, count(r) AS friends
    ORDER BY count(r) DESC                                                                                                                              
    RETURN name, friends
$$) AS (name agtype, influence agtype);
```
- Return of this query

```
  name    | influence
-----------+-----------
 "Bob"     | 3
 "Charlie" | 3
 "David"   | 3
 "Alice"   | 2
 "Eve"     | 1
(5 rows)
```
## Conclusion

In conclusion, the Cypher query language provides a powerful tool for analyzing graph data in graph databases. The example query presented here demonstrates how to calculate the influence of nodes in a social network based on their number of friends. By sorting the results in descending order, we can identify the most influential individuals in the network. This type of analysis can be useful in a variety of applications, including targeted marketing, social interventions, and network optimization. With the increasing prevalence of network data in various fields, mastering the use of Cypher and other graph query languages can provide researchers and analysts with valuable insights into complex systems.

References: 
[Apache AGE](age.apache.org/age-manual/master/intro/setup.html)
[Stackoverflow Question](https://stackoverflow.com/questions/76123775/is-there-a-way-to-determine-degree-centrality-of-an-apache-age-graph/)