Calling ggplot from Rserve. Blank png image of 1KB [duplicate]

Question

I have been working with r,rserve and ggplot of late.

This piece of code when executed in R console directly renders a chart with two bars as expected. png(file='Yash_GenderVsTotalAccountBalance.png',width=400,height=350,res=72) ggplot(data=YashCustomersAccounts, aes(x=GENDER_DESC,y=ACCOUNT_BALANCE)) + geom_bar(stat='identity') dev.off()

But when I call the same code(involving ggplot calls) from JAVA using Rserve it creates a blank png. Code is as below.

package RRnD;
import java.awt.*;
import org.rosuda.REngine.*;
import org.rosuda.REngine.Rserve.*;

public class PlottingGenderVsTotalAccountBalance {

    public static void main(String[] args) throws RserveException {
        try {
            RConnection c = new RConnection(); // make a new local connection on default port (6311)
            System.out.println("1. Connection created ----------------------------------------------------------------------");            
            System.out.println("Working directory = "+c.eval("getwd()").asString());
            System.out.println("2. Working dir read ----------------------------------------------------------------------");
            c.eval("YashCustomers <- read.csv('YashCustomer.csv', header=TRUE)");
            c.eval("YashAccounts <- read.csv('YashAccount.csv', header=TRUE)");
            c.eval("YashCustomersAccounts <- merge(YashCustomers,YashAccounts, by='CUSTOMER_ID')");
            System.out.println("3. Data.frames read ----------------------------------------------------------------------");

            c.eval("library(ggplot2)");
            c.eval("require(ggplot2)");
            System.out.println("4. ggplot2 loaded ----------------------------------------------------------------------");

            c.eval("png(file='Yash_GenderVsTotalAccountBalance.png',width=400,height=350,res=72)");
            c.parseAndEval("ggplot(data=YashCustomersAccounts, aes(x=GENDER_DESC,y=ACCOUNT_BALANCE)) + geom_bar(stat='identity');dev.off()");            
            System.out.println("5. plotting done ----------------------------------------------------------------------");

            REXP xp = c.parseAndEval("r=readBin('Yash_GenderVsTotalAccountBalance.png','raw',1024*1024)");
            c.parseAndEval("unlink('Yash_GenderVsTotalAccountBalance.jpg'); r");
            Image img = Toolkit.getDefaultToolkit().createImage(xp.asBytes());
            System.out.println("img = "+img);
            System.out.println("6. File reading done ----------------------------------------------------------------------");

            System.out.println("10. All done ----------------------------------------------------------------------");            
            c.close();
        } catch (REngineException ree) {
            System.out.println("REngineException ...");
            System.out.println(ree.getMessage());
        } catch (Exception e) {
            System.out.println("Exception ...");
            System.out.println(e.getMessage());
        }
    }

}

NOTE:- Instead of ggplot call, if I make a simple plot call like the following line, it works fine. png image is created properly. c.parseAndEval("plot(YashCustomers['CUSTOMER_ID']);dev.off()"); ... instead of ... c.parseAndEval("ggplot(data=YashCustomersAccounts, aes(x=GENDER_DESC,y=ACCOUNT_BALANCE)) + geom_bar(stat='identity');dev.off()");

Kindly help me in finding the issue. Many thanks, --Yash

Answer 1

In console ggplot draws the image automatically. But while calling ggplot plotting from Rserver we need to explicitly print the image.

c.parseAndEval("print(ggplot(data=YashCustomersAccounts, aes(x=GENDER_DESC,y=ACCOUNT_BALANCE)) + geom_bar(stat='identity'));dev.off()");