Time intervals creation, printing, and some arithmetic.
time1 - time2 difftime(time1, time2, tz, units = c("auto", "secs", "mins", "hours", "days", "weeks")) as.difftime(tim, format = "%X", units = "auto") ## S3 method for class 'difftime': format((x, ...)) ## S3 method for class 'difftime': units((x)) ## S3 replacement method for class 'difftime': units((x) <- value) ## S3 method for class 'difftime': as.double((x, units = "auto", ...) ## Group methods, notably for round(), signif(), floor(), ## ceiling(), trunc(), abs(); called directly, *not* as Math():) ## S3 method for class 'difftime': Math((x, ...))
- time1, time2
- date-time or date objects.
- an optional timezone specification to be used for the conversion, mainly for
- character string. Units in which the results are desired. Can be abbreviated.
- character string. Like
units, except that abbreviations are not allowed.
- character string or numeric value specifying a time interval.
- character specifying the format of
strptime. The default is a locale-specific time format.
- an object inheriting from class
- arguments to be passed to or from other methods.
difftime calculates a difference of two date/time objects and returns an object of class
"difftime" with an attribute indicating the units. The
Math group method provides
sign methods for objects of this class, and there are methods for the group-generic (see
Ops) logical and arithmetic operations.
units = "auto", a suitable set of units is chosen, the largest possible (excluding
"weeks") in which all the absolute differences are greater than one.
Subtraction of date-time objects gives an object of this class, by calling
units = "auto". Alternatively,
as.difftime() works on character-coded or numeric time intervals; in the latter case, units must be specified, and
format has no effect.
Limited arithmetic is available on
"difftime" objects: they can be added or subtracted, and multiplied or divided by a numeric vector. In addition, adding or subtracting a numeric vector by a
"difftime" object implicitly converts the numeric vector to a
"difftime" object with the same units as the
"difftime" object. There are methods for
sum (via the
Summary group generic).
The units of a
"difftime" object can be extracted by the
units function, which also has a replacement form. If the units are changed, the numerical value is scaled accordingly. The replacement version keeps attributes such as names and dimensions.
format method simply formats the numeric value and appends the units as a text string.
The default behaviour when
time2 was a
"POSIXlt" object changed in R 2.12.0: previously such objects were regarded as in the timezone given by
tz which defaulted to the current timezone.
(z <- Sys.time() - 3600) Sys.time() - z # just over 3600 seconds. ## time interval between releases of R 1.2.2 and 1.2.3. ISOdate(2001, 4, 26) - ISOdate(2001, 2, 26) as.difftime(c("0:3:20", "11:23:15")) as.difftime(c("3:20", "23:15", "2:"), format= "%H:%M") # 3rd gives NA (z <- as.difftime(c(0,30,60), units = "mins")) as.numeric(z, units = "secs") as.numeric(z, units = "hours") format(z)
Documentation reproduced from R 3.0.2. License: GPL-2.