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.

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)
#> <time_point<sys><second>[2]> #> [1] "1970-01-02 00:00:01" "1969-12-30 23:59:59"
#> <time_point<sys><day>[2]> #> [1] "1970-01-02" "1969-12-31"
as_sys_time(floor)
#> <time_point<sys><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