Round                  package:base                  R Documentation

Rounding of Numbers

Description:

     `ceiling' takes a single numeric argument `x' and returns a
     numeric vector containing the smallest integers not less than the
     corresponding elements of `x'.

     `floor' takes a single numeric argument `x' and returns a numeric
     vector containing the largest integers not greater than the
     corresponding elements of `x'.

     `round' rounds the values in its first argument to the specified
     number of decimal places (default 0). Note that for rounding off a
     5, the IEEE standard is used, ``go to the even digit''. Therefore
     `round(0.5)' is `0' and `round(-1.5)' is `-2'.

     `signif' rounds the values in its first argument to the specified
     number of significant digits.

     `trunc' takes a single numeric argument `x' and returns a numeric
     vector containing the integers by truncating the values in `x'
     toward `0'.

     `zapsmall' determines a `digits' argument `dr' for calling
     `round(x, digits = dr)' such that values ``close to zero'' values
     are ``zapped'', i.e., treated as `0'.

Usage:

     ceiling(x)
     floor(x)
     round(x, digits = 0)
     signif(x, digits = 6)
     trunc(x)
     zapsmall(x, digits= getOption("digits"))

Arguments:

       x: a numeric vector.

  digits: integer indicating the precision to be used.

See Also:

     `as.integer'.

Examples:

     round(.5 + -2:4) # IEEE rounding: -2  0  0  2  2  4  4
     ( x1 <- seq(-2, 4, by = .5) )
     round(x1)#-- IEEE rounding !
     x1[trunc(x1) != floor(x1)]
     x1[round(x1) != floor(x1 + .5)]
     (non.int <- ceiling(x1) != floor(x1))
     stopifnot(
      trunc(x1) == as.integer(x1),
      non.int == (ceiling(x1) != trunc(x1) | trunc(x1) != floor(x1)),
      (signif(x1, 1) != round(x1,1)) == (non.int & abs(x1) > 1)
     )

     x2 <- pi * 100^(-1:3)
     round(x2, 3)
     signif(x2, 3)

     print   (x2 / 1000, digits=4)
     zapsmall(x2 / 1000, digits=4)
     zapsmall(exp(1i*0:4*pi/2))

