Update R Programming in HPC documentation

R_usage.md

@@ -2,28 +2,37 @@ R Programming in HPC
 ====================
 
 ## What is R?
-R is a programming language and a software environment for statistical computing and graphics techniques. This is widely used now a days by statisticians and data miners for developing software tools required for data analysis. The R language is primarily derived from the S language developed at Bell Laboratories in 1975. R provides various tools and techniques for linear and nonlinear modelling, statistical tests, time series analysis, classification, clustering etc. More history and documentation of R are available at this [link](https://cran.r-project.org/manuals.html)
+R is a programming language and a software environment for statistical computing and graphics techniques. This is widely used nowadays by statisticians and data miners for developing software tools required for data analysis. The R language is primarily derived from the S language developed at Bell Laboratories in 1975. R provides various tools and techniques for linear and nonlinear modelling, statistical tests, time series analysis, classification, clustering, etc. More history and documentation of R are available at this [link](https://cran.r-project.org/manuals.html)
 ## How to run R?
-First login to one of the CARC machines via SSH.
+First, login to one of the CARC machines via SSH.
 
-`ssh -X user@machine_name.alliance.unm.edu`
+`ssh user@machine_name.alliance.unm.edu`
 
-Once logged into the machine, you have to load the module which has R program files. 
+Once logged into the machine, load the default version of R provided by the CARC machine with: 
 
-`module load r-3.5.0-gcc-4.8.5-python2-khqxja7`
+`module load r`
+
+If you would like to see all available versions of R, run:
+
+`module spider r`
+
+To also load a specific version of R, use:
+
+`module load r/<version>`
+
+Note: Some versions of R may have compiler dependencies and require a compiler module such as GCC to be loaded first. If these dependencies are needed, the module system will display an error message when attempting to load the R module that includes a `module spider r/<version>` command that will help identify the required modules.
 
 After loading the R module, begin R programming by typing
 
-`R`
+`srun --pty R`
 
-This will shows
+This will show
 
 ```bash
 
-R version 3.5.0 (2018-04-23) -- "Joy in Playing"
-Copyright (C) 2018 The R Foundation for Statistical
-Computing
-Platform: x86_64-pc-linux-gnu (64-bit)
+R version 4.4.0 (2024-04-24) -- "Puppy Cup"
+Copyright (C) 2024 The R Foundation for Statistical Computing
+Platform: x86_64-pc-linux-gnu
 
 R is free software and comes with ABSOLUTELY NO WARRANTY.
 You are welcome to redistribute it under certain conditions.
@@ -40,40 +49,42 @@ Type 'demo()' for some demos, 'help()' for on-line help, or
 Type 'q()' to quit R.
 
 ```
-This means the R module is loaded and you are ready to use R for your research
+This means the R module is loaded, and you are ready to use R for your research
 ## Running a sample script example.R 
-Let us look a sample script, example.R which will print "Hello World"
+Let us look at a sample script called "example.R" which will print "Hello World".
 The script looks like 
 
 ```bash
+# example.R
 # Program to print Hello World
 
 print('Hello World')
 ```
-In order to execute this script, type
+Before running the script, make sure you have exited the R interpreter (indicated by the `>` prompt) by typing `q()` and returning back to the Linux command line. In order to execute this script, type
 
 `Rscript example.R`
 
 This will give an output of
 
 `[1] "Hello World"`
 
-If you want to generate samples from a normal distribution, you can use the `rnorm()` function. Let's make some change to the example.R script. 
+If you want to generate samples from a normal distribution, you can use the `rnorm()` function. Let's make some changes to the example.R script. 
 
 ```bash
 # Program to print Hello World and to generate normal random numbers
 
 print('Hello World')
 
-#Calling the rnorm() function to generate three random numbers from a 
-normal distribution with mean 5 and a standard  deviation of 5
+# Calling the rnorm() function to generate three random numbers from a 
+# normal distribution with mean 5 and a standard  deviation of 5
 
 rnorm(3,mean=5,sd=5)
 ```
 
-Execute the script again and the look at the new output.
+Execute the script again and look at the new output.
 
 ```bash
 [1] "Hello World"
 [1] 3.744463 7.954163 3.363275
-```
+```
+