A simple command-line tool for evaluating mathematical expressions.

math.R

#!/usr/bin/env Rscript

suppressPackageStartupMessages(library(optparse))

opt.list <- list(
     make_option(c('-r','--round'), type = 'integer', default = 2, metavar = 'INTEGER',
     help = 'Number of decimal places (default is %default)')
)

opt.parser <- OptionParser(option_list = opt.list,
                           usage = 'usage: %prog <expression>\n',
                           description = paste0('Evaluates a mathematical expression.\n\n',
                           'Arguments:\n',
                           '\t<expression>\n',
                           '\t\tA mathematical expression to evaluate (e.g., \"5/10\")'))

arguments <- parse_args(opt.parser, positional_arguments = 1)
pos.args <- arguments$args
opt.args <- arguments$options

math.str <- pos.args[1]
n.digits <- opt.args$round

result <- round(eval(parse(text = math.str)), n.digits)
cat(result, fill = T)

Examples

For help, type:

$ math.R --help

You should see:

Usage: math.R <expression>

Evaluates a mathematical expression.

Arguments:
	<expression>
		A mathematical expression to evaluate (e.g., "5/10")

Options:
	-r INTEGER, --round=INTEGER
		Number of decimal places (default is 2)

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

To evaluate an expression, type:

$ math.R 6/7*100

85.71

By default floats are rounded to two decimal places, but you can change that. For example:

$ math.R 6/7*100 -r 3

85.714