I have 2 data sets, one contains my data and the other contains the sunrise/sunset data from the NAVY Observatory.
head(tagdata)
X ID ex2 meanlat meanlong meanEast meanNorth meandepth rec numhits species depthcat Date Time
1 1 34931 2015-07-31 13:06:26 18.34127 -64.98051 290711.7 2029082 NA 10 42 Lutjanus synagris NA 2015-07-31 13:06:26
2 2 34931 2015-07-31 14:06:26 18.34141 -64.98054 290708.6 2029097 NA 10 55 Lutjanus synagris NA 2015-07-31 14:06:26
3 3 34931 2015-07-31 15:06:26 18.34115 -64.98023 290741.3 2029068 NA 9 53 Lutjanus synagris NA 2015-07-31 15:06:26
4 4 34931 2015-07-31 16:06:26 18.34158 -64.98012 290753.0 2029115 NA 9 38 Lutjanus synagris NA 2015-07-31 16:06:26
5 5 34931 2015-07-31 17:06:26 18.34162 -64.97979 290788.0 2029119 NA 8 32 Lutjanus synagris NA 2015-07-31 17:06:26
6 6 34931 2015-07-31 18:06:26 18.34102 -64.97949 290818.5 2029053 NA 6 27 Lutjanus synagris NA 2015-07-31 18:06:26
head(AstroSun)
Date Srise Sset Sunrise_date Sunset_date Astro_Begin Astro_End ABegin_date AEnd_date
1 2015-01-01 652 1755 2015-01-01 06:52:00 2015-01-01 17:55:00 534 1913 2015-01-01 05:34:00 2015-01-01 19:13:00
2 2015-01-02 652 1756 2015-01-02 06:52:00 2015-01-02 17:56:00 534 1913 2015-01-02 05:34:00 2015-01-02 19:13:00
3 2015-01-03 652 1756 2015-01-03 06:52:00 2015-01-03 17:56:00 535 1914 2015-01-03 05:35:00 2015-01-03 19:14:00
4 2015-01-04 653 1757 2015-01-04 06:53:00 2015-01-04 17:57:00 535 1914 2015-01-04 05:35:00 2015-01-04 19:14:00
5 2015-01-05 653 1757 2015-01-05 06:53:00 2015-01-05 17:57:00 535 1915 2015-01-05 05:35:00 2015-01-05 19:15:00
6 2015-01-06 653 1758 2015-01-06 06:53:00 2015-01-06 17:58:00 536 1915 2015-01-06 05:36:00 2015-01-06 19:15:00
I want to merge both data sets and create a new column that adds day or night for each observation, based on the sunrise and sunset time frames from the Navy data. How do I go about it? Also, how can I add dusk and dawn to each observation, where by each observation starts an hour before sunrise or sunset and ending an hour after sunrise or sunset time?
Because daylight hours are always* contained within one calendar day, I think the best thing to do is merge your two data sets by Date and then create an interval of daylight hours for each day, then test if the tag date is within this interval.
I would do this using %within% along with lubridate::interval().
For your data, I will act as if all the dates are currently just character strings.
library(dplyr)
library(lubridate)
tagdata1 <- left_join(tagdata, AstroSun, by = "Date") %>%
mutate(Sunrise_date = ymd_hms(Sunrise_date)) %>%
mutate(Sunset_date = ymd_hms(Sunset_date)) %>%
mutate(tag_datim = ymd_hms(paste0(Date, Time))) %>%
mutate(daylight_intvl = interval(Sunrise_date, Sunset_date)) %>%
mutate(during_day = tag_datim %within% daylight_intvl)
tagdata1$during_day is a logical TRUE for a tag date/time that is during daylight hours.
You should be able to figure out dusk and dawn by using the above commands as well as + dhours(1) which adds an hour to any date/time value.
*I haven't considered any exotic Arctic circle edge cases or different timezones etc.