Querying Neo4J
In neo4jshell: Querying and Managing 'Neo4J' Databases in 'R'

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

The function neo4j_query() can be used to send a query to a local or remote Neo4J server. This function uses cypher-shell to send the query to Neo4J, and so the cypher-shell executable needs to be installed and available locally. See the README file for further information on configuration of the cypher-shell executable.

neo4j_query() takes the following arguments:

con should be a list containing three elements: address, which should be the bolt address of the Neo4J server, and uid and pwd as login credentials
qry should be a character string representing the query to be sent to Neo4J
shell_path should be the full path to the cypher-shell executable. The default value assumes that cypher-shell is already in the system path. Use path.expand() if necessary.
database specifies the database to be queried if not the default database. (For multitenancy Neo4J installations).
encryption is the encryption option passed to cypher-shell. This may be required as explicitly 'true' or 'false' for older installations.

Example, assuming a local Neo4J instance running the movies graph:

library(neo4jshell)

neo4j_local <- list(address = "bolt://localhost", uid = "neo4j", pwd = "password")
CQL <- 'MATCH (p1:Person {name: "Kevin Bacon"})-[:ACTED_IN]->(m:Movie)<-[:DIRECTED]-(p2:Person)
        RETURN p2.name AS Name, m.title AS Title'
cypher_path <- path.expand("~/neo4j-community-4.0.4/bin/cypher-shell")
neo4j_query(con = neo4j_local, qry = CQL, shell_path = cypher_path)

This query should return this dataframe:

``` {r example-output, echo = FALSE}

data.frame(Name = c("Ron Howard", "Rob Reiner", "Ron Howard"), Title = c("Frost/Nixon", "A Few Good Men", "Apollo 13"))

```

neo4j_query() accepts multiple query statements separated by ;. The function returns one of the following:

A dataframe of results if the query is a read query. If there were multiple statements, only the results of the final statement will display.
A message indicating successful execution if the query is a write query.
An error message if an error occurred. If there were multiple statements, the response for all statements will be displayed.