cat( )

Print labelled results with units to the console. cat() is a base R function.

Required Library

# cat() is part of base R — no package installation needed

Syntax

cat(...)

cat(...) concatenates and prints its arguments to the console with no formatting. Unlike print(), it does not add quotes around character strings or display [1] index prefixes, making it ideal for producing clean, readable output.

cat("Label:", value, "unit\n")

cat("Label:", value, "unit\n") is the standard pattern for reporting a named result with its unit. The \n at the end moves the cursor to a new line.

cat("Label:", signif(value, digits), "unit\n")

cat("Label:", signif(value, digits), "unit\n") rounds the value to the appropriate number of significant figures at the point of printing, while keeping the stored variable at full precision.

cat(..., sep = " ", file = "", append = FALSE)

cat(..., sep = " ", file = "", append = FALSE) exposes the optional arguments that control how and where output is written: sep sets the separator between items, while file and append redirect output to a file instead of the console.

Coding convention — always label printed results

Never print a bare variable name or call print() on a calculated value. Always use cat() with a descriptive label and the unit. A number without context is meaningless in a pharmaceutical report.

Argument Overview

Required arguments must be included when using a function while optional arguments can be included on demand.

… — items to print character | numeric | logical Required

One or more values to print, separated by commas. Items are coerced to character before printing. Common usage combines a text label, a computed value (wrapped in signif() or round()), and a unit string:

cat("Mean fill mass:", signif(X_bar, 4), "mg\n")

Use \n (newline) as the last item so the next output starts on a fresh line.

Data Types: character | numeric | logical | integer

sep — separator between items character Optional

A character string inserted between consecutive items. Default is a single space " ". Set sep = "" to print items with no gap, or sep = ", " for comma-separated lists.

cat("Result:", value, "mg\n")          # default: space between each item
cat("A", "B", "C", sep = "-")          # prints: A-B-C

Data Types: character · Default: ” “

file — output destination character | connection Optional

Where to send the output. Default "" prints to the console. Pass a file path string (or an open connection) to write to a file instead.

cat("Result:", signif(AV_s1, 4), "\n", file = "results.txt")

Data Types: character (file path) | connection · Default: ““ (console)

append — append to file instead of overwriting logical Optional

Only relevant when file is a file path. If TRUE, new output is appended to the end of the file. If FALSE (default), the file is overwritten.

Data Types: logical · Default: FALSE

Examples

Print a single analytical result with units

Print multiple results from a content uniformity assay

Print a pass/fail acceptance criterion

sep — custom separator between items