R: Flexible Formatting

formatC {base}

R Documentation

Flexible Formatting

Description

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

Usage

formatC(x, digits = NULL, width = NULL,
        format = NULL, flag = "", mode = NULL)
format.char(x, width = NULL, flag = "-")

Arguments

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 "d" for integers, "g" for reals.

"f" gives numbers in the usual “xxx.xxx” format; "e" and "E" give “n.dddenn” or “n.dddEnn” (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 number of significant digits. Note that this can lead to quite long result strings, see examples below.

flag

format modifier as in Kernighan and Ritchie, 2nd ed., page 243. "0" pads leading zeros; "-" does left adjustment, others are "+", " ", and "#".

mode

"double" (or "real"), "integer" or "character". Default: Automatic.

Details

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

Value

A character object of same size and attributes as x. Unlike format, each number is formatted individually. Looping over each element of x, sprintf(...) is called (inside the C function str_signif).

format.char(x) and formatC, for character x, do simple (left or right) padding with white space.

Author(s)

Originally written by Bill Dunlap, later much improved by Martin Maechler, it was first adapted for R by Friedrich Leisch.

Examples

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

format.char(c("a", "Abc", "no way"), wid = -7)  # <=> flag = "-"
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)
formatC(xx, format="fg")       # special "fixed" format.
formatC(xx, format="f", dig=80)#>> also long strings

[Package base version 0.90 ]