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Each function in concatenate returns a comma-separated string. (A length-one character vector.) They can be used to construct human-friendly messages whose elements aren’t known in advance, like calls to message, warning or stop, from clean code.


The workhorse function in concatenate is cc.

cc("one fish", "two fish")
#> [1] "one fish, two fish"

Its wrappers cc_or and cc_and insert “or” and “and” between the last two elements of the input.

cc_and("this", "that", "the other")
#> [1] "this, that and the other"
cc_or("one way", "another")
#> [1] "one way or another"

cn and its derivatives combine these functions with sprintf-like substitution and the grammatical number awareness of ngettext.

x <- unique(iris$Species)
cn_and(x, "a single species: %c", "%n unique species: %c")
#> [1] "3 unique species: setosa, versicolor and virginica"

There are row-wise data.frame methods for the cn functions.

singular <- "%n row: %c"
plural <- "%n rows whose values are %c"
cn(chickwts[1, ], singular, plural)
#> [1] "1 row: 179, horsebean"
cn_and(chickwts[1:3, 1, drop = FALSE], singular, plural)
#> [1] "3 rows whose values are 179, 160 and 136"

The cc functions are also available as binary infix operators.

x <- "important value"
x %+% "!"
#> [1] "important value!"