formatC {base}R Documentation

Formatting Using C-style Formats


Formatting numbers individually and flexibly, using C style format specifications.


formatC(x, digits = NULL, width = NULL,
        format = NULL, flag = "", mode = NULL,
        big.mark = "", big.interval = 3,
      small.mark = "", small.interval = 5,
    decimal.mark = ".")

prettyNum(x, big.mark = "",   big.interval = 3,
           small.mark = "", small.interval = 5,
         decimal.mark = ".", ...)


x an atomic numerical or character object, typically a vector of real numbers.
digits the desired number of digits after the decimal point (format = "f") or significant digits (format = "g", = "e" or = "fg").
Default: 2 for integer, 4 for real numbers. If less than 0, the C default of 6 digits is used.
width the total field width; if both digits and width are unspecified, width defaults to 1, otherwise to digits + 1. width = 0 will use width = digits, width < 0 means left justify the number in this field (equivalent to flag ="-"). If necessary, the result will have more characters than width.
format equal to "d" (for integers), "f", "e", "E", "g", "G", "fg" (for reals), or "s" (for strings). Default is "d" for integers, "g" for reals.
"f" gives numbers in the usual format; "e" and "E" give n.ddde+nn or n.dddE+nn (scientific format); "g" and "G" put x[i] into scientific format only if it saves space to do so.
"fg" uses fixed format as "f", but digits as the minimum number of significant digits. That this can lead to quite long result strings, see examples below. Note that unlike signif this prints large numbers with more significant digits than digits.
flag For formatC, a character string giving a format modifier as in Kernighan and Ritchie (1988, page 243). "0" pads leading zeros; "-" does left adjustment, others are "+", " ", and "#". There can be more than one of these, in any order.
mode "double" (or "real"), "integer" or "character". Default: Determined from the storage mode of x.
big.mark character; if not empty used as mark between every big.interval decimals before (hence big) the decimal point.
big.interval see big.mark above; defaults to 3.
small.mark character; if not empty used as mark between every small.interval decimals after (hence small) the decimal point.
small.interval see small.mark above; defaults to 5.
decimal.mark the character to be used to indicate the numeric decimal point.
... arguments passed to format.


If you set format it overrides the setting of mode, so formatC(123.45, mode="double", format="d") gives 123.

The rendering of scientific format is platform-dependent: some systems use n.ddde+nnn or n.dddenn rather than n.ddde+nn.

formatC does not necessarily align the numbers on the decimal point, so formatC(c(6.11, 13.1), digits=2, format="fg") gives c("6.1", " 13"). If you want common formatting for several numbers, use format.

prettyNum is the utility function for prettifying x. If x is not a character, format(x[i], ...) is applied to each element, and then it is left unchanged if all the other arguments are at their defaults. Note that prettyNum(x) may behave unexpectedly if x is a character vector not resulting from something like format(<number>): in particular it assumes that a period is a decimal mark.


A character object of same size and attributes as x. Unlike format, each number is formatted individually. Looping over each element of x, the C function sprintf(...) is called (inside the C function str_signif).
formatC: for character x, do simple (left or right) padding with white space.


formatC was originally written by Bill Dunlap, later much improved by Martin Maechler. It was first adapted for R by Friedrich Leisch.


Kernighan, B. W. and Ritchie, D. M. (1988) The C Programming Language. Second edition. Prentice Hall.

See Also


sprintf for more general C like formatting.


xx  <- pi * 10^(-5:4)
cbind(format(xx, digits=4), formatC(xx))
cbind(formatC(xx, wid = 9, flag = "-"))
cbind(formatC(xx, dig = 5, wid = 8, format = "f", flag = "0"))
cbind(format(xx, digits=4), formatC(xx, dig = 4, format = "fg"))

formatC(    c("a", "Abc", "no way"), wid = -7)  # <=> flag = "-"
formatC(c((-1:1)/0,c(1,100)*pi), wid=8, dig=1)

xx <- c(1e-12,-3.98765e-10,1.45645e-69,1e-70,pi*1e37,3.44e4)
##       1        2             3        4      5       6
formatC(xx, format="fg")       # special "fixed" format.
formatC(xx, format="f", dig=80)#>> also long strings

r <- c("76491283764.97430", "29.12345678901", "-7.1234", "-100.1","1123")
## American:
prettyNum(r, big.mark = ",")
## Some Europeans:
prettyNum(r, big.mark = "'", decimal.mark = ",")

(dd <- sapply(1:10, function(i)paste((9:0)[1:i],collapse="")))
prettyNum(dd, big.mark="'")

## examples of 'small.mark'
pN <- stats::pnorm(1:7, lower=FALSE)
cbind(format (pN, small.mark = " ", digits = 15))
cbind(formatC(pN, small.mark = " ", digits = 17, format = "f"))

[Package base version 2.2.1 Index]