rdatautil

Utility to read and write RData (rds) files in java.

RDS files are created in R:

# Save a data.frame object to a file
saveRDS(mtcars, "mtcars.rds")

...and they can be read in R like this:

# Restore it 
my_data <- readRDS("mtcars.rds")

This utility allows you to save and read such rsd files in java. It relies on the Renjin project for the heavy lifting.

Usage

Add the dependency to your pom (or equivalent):

<dependency>
    <groupId>se.alipsa</groupId>
    <artifactId>rdatautil</artifactId>
    <version>1.0.0</version>
</dependency>

Read a rds file

the read method takes either a File or an InputStream as a parameter:

import se.alipsa.rdatautils.RDataUtil;
import org.renjin.sexp.SEXP;

SEXP data = RDataUtil.read(new File("mtcars.rds"));

import se.alipsa.rdatautils.RDataUtil;
import org.renjin.sexp.SEXP;

SEXP data = RDataUtil.read(getClass().getResourceAsStream("mtcars.rds"));

Write to a rds file

import se.alipsa.rdatautils.RDataUtil;
import org.renjin.sexp.SEXP;
import org.renjin.sexp.PairList;

PairList.Builder file = new PairList.Builder();
file.add("names", new StringArrayVector("Kurt", "Susan", "Zoe", StringVector.NA));
file.add("income", new IntArrayVector(120000, 220202, 303030, IntVector.NA));
SEXP sexp = file.build();

// You can write to a file
RDataUtil.write(sexp, new File("employeeSalaries.rds"));

// or an OutputStream
RDataUtil.write(sexp, System.out);

Handling complex data

The se.alipsa:renjin-client-data-utils project enables you to deal with tabular data and combines very well with rdatautil:

Reading data:

import se.alipsa.rdatautils.RDataUtil;
import org.renjin.sexp.SEXP;
import se.alipsa.renjin.client.datautils.Table;

SEXP data = RDataUtil.read(getClass().getResourceAsStream("employeeSalaries.rds"));
Table table = Table.createTable(data);
// Get the data.frame as a List of rows suitable for how data is usually handled in java:
List<List<Object>> rows = table.getRowList();

// You can also get an individual value
String employee1 = table.getValueAsString(0,0);

Writing data:

import se.alipsa.rdatautils.RDataUtil;
import org.renjin.sexp.SEXP;
import se.alipsa.renjin.client.datautils.Table;
import java.sql.ResultSet;
import java.sql.SQLException;

class RdataSaver {
  
    public static void saveToRds(ResultSet rs, OutputStream os) throws SQLException {
        Table table = new Table(rs);
        RDataUtil.write(table.asDataframe(), os);
    }
}