How to Write and Execute a Hello World Program in File for R

How to write and execute a hello world program in file for R?

I general you want to give your R files the .R extension.

To run a program you can start R (by typing "R" at the command prompt) and once inside the program/interpreter, you can execute your program (let's call it "so.R") with the source command. E.g.,

> source('so.R')

yields:

Hello World 

You can run the program from the Unix shell with

R CMD BATCH so.R

it will generate a file named "so.Rout" that will contain the output of your program run, especially if it contains non-trivial amounts of output. If there is a problem with the program run, the error messages etc will also be in this file so it's a good diagnostic tool. An alternative is the Rscript command which sends its output to stdout, in which case if it's long you need to capture it yourself.

There is a very useful trick, when googling for R related topics it can be tricky because R is a single character. To be effective, pre-pend "r-help:" to your search terms. E.g.,

r-help:Running a program

Here are two manuals that might be useful/help you get started:

• Introduction to R
• Programming in R

and also take a look at The R Manuals.

More information/FAQs, etc., can be found at the R web site itself. I have found that there is a lot of information on R (esp tutorials etc), but it can be tricky to find them. The "r-help" google trick really helps with this.

R from C -- Simplest Possible Helloworld

You want to call R from C?

Look at section 8.1 in the Writing R Extensions manual. You should also look into the "tests" directory (download the source package extract it and you'll have the tests directory). A similar question was previously asked on R-Help and here was the example:

#include <Rinternals.h> 
#include <Rembedded.h> 

SEXP hello() { 
  return mkString("Hello, world!\n"); 
} 

int main(int argc, char **argv) { 
  SEXP x; 
  Rf_initEmbeddedR(argc, argv); 
  x = hello(); 
  return x == NULL;             /* i.e. 0 on success */ 
} 

The simple example from the R manual is like so:

 #include <Rembedded.h>

 int main(int ac, char **av)
 {
     /* do some setup */
     Rf_initEmbeddedR(argc, argv);
     /* do some more setup */

     /* submit some code to R, which is done interactively via
         run_Rmainloop();

         A possible substitute for a pseudo-console is

         R_ReplDLLinit();
         while(R_ReplDLLdo1() > 0) {
           add user actions here if desired
         }
      */
     Rf_endEmbeddedR(0);
     /* final tidying up after R is shutdown */
     return 0;
 }

Incidentally, you might want to consider using Rinside instead: Dirk provides a nice "hello world" example on the project homepage.

In you're interested in calling C from R, here's my original answer:

This isn't exactly "hello world", but here are some good resources:

• Jay Emerson recently gave a talk on R package development at the New York useR group, and he provided some very nice examples of using C from within R. Have a look at the paper from this discussion on his website, starting on page 9. All the related source code is here: http://www.stat.yale.edu/~jay/Rmeetup/MyToolkitWithC/.
• The course taught at Harvard by Gopi Goswami in 2005: C-C++-R (in Statistics). This includes extensive examples and source code.

Write lines of text to a file in R

fileConn<-file("output.txt")
writeLines(c("Hello","World"), fileConn)
close(fileConn)

Execute a program that prints hello world from another program in java

Each java application runs in it's own console. The console you see when launching your program belongs to Command.java. This means it will only show output from Command.java and nothing else. New.java runs in a different console that in this case is not shown to you. The second version of Command.java reads the output from New.java and then prints it to it's own console.

How do I create a ruby Hello world?

If you are talking about a command line program this will work.

puts "Hello World"

or if you want an object oriented version

class HelloWorld
   def initialize(name)
      @name = name.capitalize
   end
   def sayHi
      puts "Hello #{@name}!"
   end
end

hello = HelloWorld.new("World")
hello.sayHi

If you are looking for a ruby on rails version of Hello World.
Check the Getting Started Guide for Rails.

How to Make my R script executable?

Ah, Its carriage return (\r) issue, It's added to the first line, if you are using vi editor, :set list will show it. line endings will be shown as $ and carriage return chars as ^M.

#!/usr/bin/env Rscript  Makes your script portable than #!/usr/bin/Rscript

Btw, you can insert \r in vi by going into insert(i)/Append(a) mode and type ctrl+v and then ctrl+m

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