Date and Time

Load Packages

library(tidyverse) 
# install.packages("lubridate")
library(lubridate)
library(nycflights13)
library(openair)

Get today’s date and time

today()

## [1] "2022-08-18"

now()

## [1] "2022-08-18 00:05:33 CST"

Create a date time object from a string

ymd("2022-01-31")

## [1] "2022-01-31"

mdy("January 31st, 2022")

## [1] "2022-01-31"

dmy("31-Jan-2022")

## [1] "2022-01-31"

ymd_hms("2022-01-31 20:11:59")

## [1] "2022-01-31 20:11:59 UTC"

Create a date time object from individual components

glimpse(flights)

## Rows: 336,776
## Columns: 19
## $ year           <int> 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2013, 2…
## $ month          <int> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1…
## $ day            <int> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1…
## $ dep_time       <int> 517, 533, 542, 544, 554, 554, 555, 557, 557, 558, 558, …
## $ sched_dep_time <int> 515, 529, 540, 545, 600, 558, 600, 600, 600, 600, 600, …
## $ dep_delay      <dbl> 2, 4, 2, -1, -6, -4, -5, -3, -3, -2, -2, -2, -2, -2, -1…
## $ arr_time       <int> 830, 850, 923, 1004, 812, 740, 913, 709, 838, 753, 849,…
## $ sched_arr_time <int> 819, 830, 850, 1022, 837, 728, 854, 723, 846, 745, 851,…
## $ arr_delay      <dbl> 11, 20, 33, -18, -25, 12, 19, -14, -8, 8, -2, -3, 7, -1…
## $ carrier        <chr> "UA", "UA", "AA", "B6", "DL", "UA", "B6", "EV", "B6", "…
## $ flight         <int> 1545, 1714, 1141, 725, 461, 1696, 507, 5708, 79, 301, 4…
## $ tailnum        <chr> "N14228", "N24211", "N619AA", "N804JB", "N668DN", "N394…
## $ origin         <chr> "EWR", "LGA", "JFK", "JFK", "LGA", "EWR", "EWR", "LGA",…
## $ dest           <chr> "IAH", "IAH", "MIA", "BQN", "ATL", "ORD", "FLL", "IAD",…
## $ air_time       <dbl> 227, 227, 160, 183, 116, 150, 158, 53, 140, 138, 149, 1…
## $ distance       <dbl> 1400, 1416, 1089, 1576, 762, 719, 1065, 229, 944, 733, …
## $ hour           <dbl> 5, 5, 5, 5, 6, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 5, 6, 6, 6…
## $ minute         <dbl> 15, 29, 40, 45, 0, 58, 0, 0, 0, 0, 0, 0, 0, 0, 0, 59, 0…
## $ time_hour      <dttm> 2013-01-01 05:00:00, 2013-01-01 05:00:00, 2013-01-01 0…

new_flights <- flights %>% 
  select(year, month, day, hour, minute)

new_flights_date <- new_flights %>% 
  mutate(departure = make_datetime(year, month, day, hour, minute))

From other types

as_datetime(now())

## [1] "2022-08-17 16:05:36 UTC"

as_date(now())

## [1] "2022-08-18"

Quiz 1

d1 <- mdy("January 1, 2010")

d2 <- ymd("2015-Mar-07")

d3 <- dmy("06-Jun-2017")

d4 <- mdy(c("August 19 (2015)", "July 1 (2015)"))

d5 <- mdy("12/30/14") 

Quiz 2

ymd(c("2010-10-10", "bananas"))

## Warning: 1 failed to parse.

## [1] "2010-10-10" NA

Manipulating date and time

datetime <- ymd_hms("2022/Jul/08 12:34:56")
year(datetime)

## [1] 2022

month(datetime)

## [1] 7

mday(datetime)

## [1] 8

yday(datetime)

## [1] 189

wday(datetime)

## [1] 6

Date time components

month(datetime, label = TRUE, abbr = FALSE)

## [1] July
## 12 Levels: January < February < March < April < May < June < ... < December

wday(datetime)

## [1] 6

hour(datetime)

## [1] 12

minute(datetime)

## [1] 34

second(datetime)

## [1] 56

Rounding

datetime <- "2022-Jul-08 12:34:56"
datetime <- ymd_hms(datetime)
ceiling_date(datetime, "min")

## [1] "2022-07-08 12:35:00 UTC"

floor_date(datetime, "hour")

## [1] "2022-07-08 12:00:00 UTC"

round_date(datetime, "month")

## [1] "2022-07-01 UTC"

Setting components

(datetime <- ymd_hms("2020-Jul-08 12:34:56"))

## [1] "2020-07-08 12:34:56 UTC"

year(datetime) <- 2022
datetime

## [1] "2022-07-08 12:34:56 UTC"

month(datetime) <- 08
datetime

## [1] "2022-08-08 12:34:56 UTC"

hour(datetime) <- hour(datetime) + 2
datetime

## [1] "2022-08-08 14:34:56 UTC"

Using update()

(datetime <- ymd_hms("2020-Jul-08 12:34:56"))

## [1] "2020-07-08 12:34:56 UTC"

update(datetime, year = 2022, month = 08, mday = 12, hour = 21)

## [1] "2022-08-12 21:34:56 UTC"

Quiz 3

# install.packages("openair")
library(openair)
our_new_dataset <- openair::mydata %>% 
  head(50)

our_new_mutated_dataset <- our_new_dataset %>% 
  mutate(year_new_column = year(date), 
         month_new_column = month(date),
         day_new_column = mday(date))

year(our_new_mutated_dataset$date) <- 2022

Durations

my_age <- today() - ymd("1995-03-27")
my_age

## Time difference of 10006 days

as.duration(my_age)

## [1] "864518400s (~27.39 years)"

Different durations

dseconds(15)

## [1] "15s"

dminutes(10)

## [1] "600s (~10 minutes)"

dhours(c(12, 24))

## [1] "43200s (~12 hours)" "86400s (~1 days)"

ddays(0:5)

## [1] "0s"                "86400s (~1 days)"  "172800s (~2 days)"
## [4] "259200s (~3 days)" "345600s (~4 days)" "432000s (~5 days)"

dweeks(3)

## [1] "1814400s (~3 weeks)"

dyears(1)

## [1] "31557600s (~1 years)"

Airthmetic with Durations

2 * dyears(1)

## [1] "63115200s (~2 years)"

dyears(1) + dweeks(12) + dhours(15)

## [1] "38869200s (~1.23 years)"

today() + ddays(1)

## [1] "2022-08-19"

today() - dyears(1)

## [1] "2021-08-17 18:00:00 UTC"

Periods

one_pm <- ymd_hms("2022-04-12 13:00:00", tz = "America/New_York")
one_pm + ddays(1)

## [1] "2022-04-13 13:00:00 EDT"

Manipulating Periods

seconds(15)

## [1] "15S"

hours(c(12, 24))

## [1] "12H 0M 0S" "24H 0M 0S"

days(7)

## [1] "7d 0H 0M 0S"

months(1:6)

## [1] "1m 0d 0H 0M 0S" "2m 0d 0H 0M 0S" "3m 0d 0H 0M 0S" "4m 0d 0H 0M 0S"
## [5] "5m 0d 0H 0M 0S" "6m 0d 0H 0M 0S"

weeks(3)

## [1] "21d 0H 0M 0S"

Airthmetic with Periods

10 * (months(6) + days(1))

## [1] "60m 10d 0H 0M 0S"

ymd("2020-01-01") + dyears(1)

## [1] "2020-12-31 06:00:00 UTC"

Intervals

next_year <- today() + years(1)
(today() %--% next_year) / ddays(1)

## [1] 365

Available time zones

Sys.timezone()

## [1] "Asia/Taipei"

head(OlsonNames())

## [1] "Africa/Abidjan"     "Africa/Accra"       "Africa/Addis_Ababa"
## [4] "Africa/Algiers"     "Africa/Asmara"      "Africa/Asmera"

Set time zones

xa <- with_tz("2022-06-02 02:30:00", tzone = "Asia/Kolkata")
xa

## [1] "2022-06-02 IST"

xb <- force_tz(xa, tzone = "America/New_York")
xb

## [1] "2022-06-02 EDT"

xc <- mdy_hms("09/12/2021 09:00:10", tz = "Asia/Kolkata")
xc

## [1] "2021-09-12 09:00:10 IST"

Quiz 5.1

join_data_1 <- read_csv(here::here("data", "join_data1.csv"))
join_data_2 <- read_csv(here::here("data", "join_data2.csv"))

summary(join_data_1)
summary(join_data_2)

Quiz 5.3

join_data_1$date <- ymd_hms(join_data_1$date, tz = "Asia/Kolkata")
join_data_2$Date <- dmy_hms(join_data_2$Date, tz = "Asia/Kolkata")

Quiz 5.4

new_joined_df <- full_join(join_data_1, join_data_2, by = c("date" = "Date", 
                                                            "area" = "Area"))

Quiz 5.5

new_joined_df <- new_joined_df %>% 
  select(everything(), - so2)

Quiz 5.6

new_joined_df <- new_joined_df %>% 
  filter(area == "BLR")

Quiz 5.7

new_joined_df <- new_joined_df %>% 
  mutate(ratio = pm25 / pm10)

Quiz 5.8

 new_joined_df %>% 
  ggplot(aes(pm25, pm10)) + 
  geom_point()

Quiz 5.9

 new_joined_df %>% 
  ggplot(aes(date, ratio)) + 
  geom_line()