Command Line Flags in R Programming Language

Here’s the translation of the Go code to R, along with explanations in Markdown format suitable for Hugo:

R provides several packages for parsing command-line arguments. For this example, we’ll use the optparse package, which offers functionality similar to the flag package in the original example.

First, let’s install and load the optparse package:

install.packages("optparse")
library(optparse)

Now, let’s create our command-line program:

library(optparse)

# Define the command-line options
option_list <- list(
  make_option(c("-w", "--word"), type="character", default="foo",
              help="a string [default=%default]"),
  make_option(c("-n", "--numb"), type="integer", default=42,
              help="an integer [default=%default]"),
  make_option(c("-f", "--fork"), action="store_true", default=FALSE,
              help="a boolean flag [default=%default]"),
  make_option(c("-s", "--svar"), type="character", default="bar",
              help="a string variable [default=%default]")
)

# Parse the command-line arguments
opt_parser <- OptionParser(option_list=option_list)
opts <- parse_args(opt_parser)

# Print out the parsed options and any remaining arguments
cat("word:", opts$word, "\n")
cat("numb:", opts$numb, "\n")
cat("fork:", opts$fork, "\n")
cat("svar:", opts$svar, "\n")
cat("args:", paste(opts$args, collapse=" "), "\n")

To run this program, save it as command_line_flags.R and use the following command:

Rscript command_line_flags.R [options]

Here are some examples of how to use the program:

1. Run with default values:

$ Rscript command_line_flags.R
word: foo 
numb: 42 
fork: FALSE 
svar: bar 
args:

2. Provide values for all options:

$ Rscript command_line_flags.R -w opt -n 7 -f -s flag
word: opt 
numb: 7 
fork: TRUE 
svar: flag 
args:

3. Provide some options and positional arguments:

$ Rscript command_line_flags.R -w opt a1 a2 a3
word: opt 
numb: 42 
fork: FALSE 
svar: bar 
args: a1 a2 a3

4. Get help text:

$ Rscript command_line_flags.R -h
Usage: command_line_flags.R [options]

Options:
    -w CHARACTER, --word=CHARACTER
        a string [default=foo]

    -n INTEGER, --numb=INTEGER
        an integer [default=42]

    -f, --fork
        a boolean flag [default=FALSE]

    -s CHARACTER, --svar=CHARACTER
        a string variable [default=bar]

    -h, --help
        Show this help message and exit

Note that R’s optparse package handles flags differently from the original example. In R, you can mix options and positional arguments, and all non-option arguments are collected in the args field of the parsed options.

This example demonstrates how to use command-line flags in R, providing similar functionality to the original example while adhering to R’s conventions and the optparse package’s structure.