Utility function to make it easier to select periods from a data frame before sending to a function

selectByDate(mydata, start = "1/1/2008", end = "31/12/2008",
  year = 2008, month = 1, day = "weekday", hour = 1)

Arguments

mydata

A data frame containing a date field in hourly or high resolution format.

start

A start date string in the form d/m/yyyy e.g. “1/2/1999” or in ‘R’ format i.e. “YYYY-mm-dd”, “1999-02-01”

end

See start for format.

year

A year or years to select e.g. year = 1998:2004 to select 1998-2004 inclusive or year = c(1998, 2004) to select 1998 and 2004.

month

A month or months to select. Can either be numeric e.g. month = 1:6 to select months 1-6 (January to June), or by name e.g. month = c("January", "December"). Names can be abbreviated to 3 letters and be in lower or upper case.

day

A day name or or days to select. day can be numeric (1 to 31) or character. For example day = c("Monday", "Wednesday") or day = 1:10 (to select the 1st to 10th of each month). Names can be abbreviated to 3 letters and be in lower or upper case. Also accepts “weekday” (Monday - Friday) and “weekend” for convenience.

hour

An hour or hours to select from 0-23 e.g. hour = 0:12 to select hours 0 to 12 inclusive.

Details

This function makes it much easier to select periods of interest from a data frame based on dates in a British format. Selecting date/times in R format can be intimidating for new users. This function can be used to select quite complex dates simply - see examples below.

Dates are assumed to be inclusive, so start = "1/1/1999" means that times are selected from hour zero. Similarly, end = "31/12/1999" will include all hours of the 31st December. start and end can also be in standard R format as a string i.e. "YYYY-mm-dd", so start = "1999-01-01" is fine.

All options are applied in turn making it possible to select quite complex dates

Examples

## select all of 1999 data.1999 <- selectByDate(mydata, start = "1/1/1999", end = "31/12/1999") head(data.1999)
#> # A tibble: 6 x 10 #> date ws wd nox no2 o3 pm10 so2 co pm25 #> <dttm> <dbl> <int> <int> <int> <int> <int> <dbl> <dbl> <int> #> 1 1999-01-01 00:00:00 5.04 140 88 35 4 21 3.84 1.02 18 #> 2 1999-01-01 01:00:00 4.08 160 132 41 3 17 5.24 2.7 11 #> 3 1999-01-01 02:00:00 4.8 160 168 40 4 17 6.51 2.87 8 #> 4 1999-01-01 03:00:00 4.92 150 85 36 3 15 4.18 1.62 10 #> 5 1999-01-01 04:00:00 4.68 150 93 37 3 16 4.25 1.02 11 #> 6 1999-01-01 05:00:00 3.96 160 74 29 5 14 3.88 0.725 NA
tail(data.1999)
#> # A tibble: 6 x 10 #> date ws wd nox no2 o3 pm10 so2 co pm25 #> <dttm> <dbl> <int> <int> <int> <int> <int> <dbl> <dbl> <int> #> 1 1999-12-31 18:00:00 4.68 190 226 39 NA 29 5.46 2.38 23 #> 2 1999-12-31 19:00:00 3.96 180 202 37 NA 27 4.78 2.15 23 #> 3 1999-12-31 20:00:00 3.36 190 246 44 NA 30 5.88 2.45 23 #> 4 1999-12-31 21:00:00 3.72 220 231 35 NA 28 5.28 2.22 23 #> 5 1999-12-31 22:00:00 4.08 200 217 41 NA 31 4.79 2.17 26 #> 6 1999-12-31 23:00:00 3.24 200 181 37 NA 28 3.48 1.78 22
# or... data.1999 <- selectByDate(mydata, start = "1999-01-01", end = "1999-12-31") # easier way data.1999 <- selectByDate(mydata, year = 1999) # more complex use: select weekdays between the hours of 7 am to 7 pm sub.data <- selectByDate(mydata, day = "weekday", hour = 7:19) # select weekends between the hours of 7 am to 7 pm in winter (Dec, Jan, Feb) sub.data <- selectByDate(mydata, day = "weekend", hour = 7:19, month = c("dec", "jan", "feb"))