Often they're scattered across the script.

Inefficient and prone to errors.

A Better Way

Mostly this is good, but storing credentials in a script is a very bad idea!

An Even Better Way

Storing credentials in the environment is somewhat better.

Using Rscript

Write a hello-world.sh script.

The first line tells the shell what interpreter to use.

Make it executable.

$ chmod u+x hello-world.sh
                        

Run it.

$ ./hello-world.sh
Hello World!
                        

When to use Rscript?

• If you want a standalone executable.
• If configuration comes from the environment.

Using (Command Line) R

Write a hello-world.R script.

Pipe it through the R interpreter.

$ cat hello-world.R | R --slave
Hello World!
                        

When to just use R?

• If you want a script that still plays nicely in RStudio.
• If you want to launch multiple configurations.

Text Substitution

By default name is set to "World".

$ cat hello-world-variable.R | R --slave
Hello World!
                        

Sprinkle some shell magic! Use sed to substitute "useRs" in place of "World".

$ sed 's/World/useRs/' hello-world-variable.R | R --slave
Hello useRs!
                        

Environment Variables

By default name is set to "World".

$ cat hello-world-environment.R | R --slave
Hello World!
                        

Defining a NAME environment variable causes name to be set to "useRs".

$ NAME=useRs && cat hello-world-environment.R | R --slave
Hello useRs!
                        

Multiple Configurations

Changing the value of RATIO.

$ sed "s/\(^RATIO   =\).*/\1 0.25/" buffon-needle-configuration.R
# CONFIGURATION ---------------------------------------------------------------

RATIO   = 0.25
SAMPLES = 500000        # Number of times that the needle is dropped.
SEED    = 13            # Random seed for repeatability.

# -----------------------------------------------------------------------------
                        

Can change the value of SAMPLES too.

Can also change the value of both RATIO and SAMPLES.

Script It!

Wish List

1. World Peace.
2. A massive computer with
   1. 128 CPUs,
   2. 4192 RAM and
   3. a blazing fast network connection.

But I only need it for half an hour.

And my budget is $15.

Cloud Solution

If you have

• a credit card and
• a SSH client

then you can have this massive computer.

You can spin it up for just half an hour. And it'll be within budget.

Machine #1 Machine #2 CPUs 1 128 RAM (GB) 1 4192 Cost ($/hour) 0.0035 26.688