Convert a date-time to a numeric time of day.

Returns the time of day as either a proportion of the 24-hour day (0 = midnight, 0.5 = noon, 1 = next midnight) or as a decimal hour (0 = midnight, 6.5 = 6:30 AM, 23.5 = 11:30 PM). Seconds are included in the calculation.

Usage

time_of_day(times, time_format = "proportion")

Arguments

times

A POSIXct vector.

time_format

One of 'proportion' (default) or 'hour'.

Value

A numeric vector of the same length as times.

Details

This is useful for statistical analyses — for example, fitting a circular model of daily activity or finding the hour of peak buzz detections. For plotting, use commontime and label_hour instead.

See also

commontime for a POSIXct alternative suitable for plotting.

Examples

times <- as.POSIXct(
  c('2023-08-09 00:00:00', '2023-08-09 06:00:00', '2023-08-09 18:30:00'),
  tz = 'America/New_York'
)

# Midnight = 0, 6 AM = 0.25, noon = 0.5
time_of_day(times)
#> [1] 0.0000000 0.2500000 0.7708333

# As decimal hours: midnight = 0, 6 AM = 6, 6:30 PM = 18.5
time_of_day(times, time_format = 'hour')
#> [1]  0.0  6.0 18.5