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Cast a duration between precisions

Source: R/duration.R
duration_cast.Rd

Casting is one way to change a duration's precision.

Casting to a less precise precision will completely drop information that is more precise than the precision that you are casting to. It does so in a way that makes it round towards zero.

Casting to a more precise precision is done through a multiplication by a conversion factor between the current precision and the new precision.

Usage

duration_cast(x, precision)

Arguments

x

[clock_duration]

A duration.

precision

[character(1)]

A precision. One of:

  • "year"

  • "quarter"

  • "month"

  • "week"

  • "day"

  • "hour"

  • "minute"

  • "second"

  • "millisecond"

  • "microsecond"

  • "nanosecond"

Value

x cast to the new precision.

Details

When you want to change to a less precise precision, you often want duration_floor() instead of duration_cast(), as that rounds towards negative infinity, which is generally the desired behavior when working with time points (especially ones pre-1970, which are stored as negative durations).

Examples

x <- duration_seconds(c(86401, -86401))

# Casting rounds towards 0
cast <- duration_cast(x, "day")
cast
#> <duration<day>[2]>
#> [1] 1  -1

# Flooring rounds towards negative infinity
floor <- duration_floor(x, "day")
floor
#> <duration<day>[2]>
#> [1] 1  -2

# Flooring is generally more useful when working with time points,
# note that the cast ends up rounding the pre-1970 date up to the next
# day, while the post-1970 date is rounded down.
as_sys_time(x)
#> <sys_time<second>[2]>
#> [1] "1970-01-02T00:00:01" "1969-12-30T23:59:59"
as_sys_time(cast)
#> <sys_time<day>[2]>
#> [1] "1970-01-02" "1969-12-31"
as_sys_time(floor)
#> <sys_time<day>[2]>
#> [1] "1970-01-02" "1969-12-30"

# Casting to a more precise precision
duration_cast(x, "millisecond")
#> <duration<millisecond>[2]>
#> [1] 86401000  -86401000