如何在 R 的日期范围及其各自的值之间找到所有月份的第三个星期日日期

Question

For a particular date range, for example between 2020-01-29 and 2021-05-02, I want to find out dates for every 3rd Sunday of every month along with their associated value in a data.frame .

Additionally, if there is any 5th Monday in any month then I want to obtain its date and corresponding value in a separate data.frame .

Please note that it needs to be between a date range from those given in the data.frame .

## for creating data frame in R wrt dates and values
dates_seq<-(seq(as.Date("2019/12/28"), by = "day", length.out = 1000))
dates_seq<-as.data.frame(dates_seq)
values<-seq(1:1000)
df<-as.data.frame(cbind(dates_seq,values))

To summarize, I want to find the third Sunday date for every month and it's corresponding value and the fifth Monday for every month if there is any along with it's value.

Answer 1

Here's a base R approach:

# Get date between 2020-01-29 and 2021-05-0
temp <- subset(df, dates_seq >= as.Date('2020-01-29') & 
                    dates_seq <= as.Date('2021-05-02'))
#Add weekday
temp$week_day <- weekdays(temp$dates_seq)
#Add week number for each month
temp$week_number <- ave(temp$week_day, temp$week_day, 
                        format(temp$dates_seq, "%Y-%m"), FUN = seq_along)
#Subset 3rd Sunday and 5th Monday
subset(temp, week_number == 3 & week_day == 'Sunday' | 
             week_number == 5 & week_day == 'Monday')


#     dates_seq values week_day week_number
#51  2020-02-16     51   Sunday           3
#79  2020-03-15     79   Sunday           3
#94  2020-03-30     94   Monday           5
#114 2020-04-19    114   Sunday           3
#142 2020-05-17    142   Sunday           3
#177 2020-06-21    177   Sunday           3
#185 2020-06-29    185   Monday           5
#205 2020-07-19    205   Sunday           3
#233 2020-08-16    233   Sunday           3
#248 2020-08-31    248   Monday           5
#268 2020-09-20    268   Sunday           3
#296 2020-10-18    296   Sunday           3
#324 2020-11-15    324   Sunday           3
#339 2020-11-30    339   Monday           5
#359 2020-12-20    359   Sunday           3
#387 2021-01-17    387   Sunday           3
#422 2021-02-21    422   Sunday           3
#450 2021-03-21    450   Sunday           3
#458 2021-03-29    458   Monday           5
#478 2021-04-18    478   Sunday           3

Answer 2

As in lubridate Sundays are the 1st day of the week, this code will give you a data frame containing all third Sundays:

df <- df %>%
  mutate(dates_seq = as.Date(dates_seq)) %>%
  mutate(year = year(dates_seq),
         month = month(dates_seq),
         day = wday(dates_seq)) %>%
  filter(day == 1) %>%
  group_by(year, month) %>%
  slice(3)

You could do a match with the original data frame to find the row index.