era v0.5.0 is now available on CRAN:
install.packages("era")
This minor release adds functions for chronological ordering (yr_sort()) of year vectors:
# Forward-counting era: x <- yr(c(200, 100, 300), "CE") yr_earliest(x) #> # CE years <yr[1]>: #> [1] 100 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 yr_latest(x) #> # CE years <yr[1]>: #> [1] 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 yr_range(x) #> # CE years <yr[2]>: #> [1] 100 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 # Backward-counting era: y <- yr(c(200, 100, 300), "BCE") yr_earliest(y) #> # BCE years <yr[1]>: #> [1] 300 #> # Era: Before Common Era (BCE): Gregorian years (365.2425 days), counted backwards from 1 yr_latest(y) #> # BCE years <yr[1]>: #> [1] 100 #> # Era: Before Common Era (BCE): Gregorian years (365.2425 days), counted backwards from 1 yr_range(x) #> # CE years <yr[2]>: #> [1] 100 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0
And for calculating their extreme values (yr_earliest(), yr_latest(), and yr_range())
# Forward-counting era: x <- yr(c(200, 100, 300), "CE") yr_earliest(x) #> # CE years <yr[1]>: #> [1] 100 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 yr_latest(x) #> # CE years <yr[1]>: #> [1] 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 yr_range(x) #> # CE years <yr[2]>: #> [1] 100 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0 # Backward-counting era: y <- yr(c(200, 100, 300), "BCE") yr_earliest(y) #> # BCE years <yr[1]>: #> [1] 300 #> # Era: Before Common Era (BCE): Gregorian years (365.2425 days), counted backwards from 1 yr_latest(y) #> # BCE years <yr[1]>: #> [1] 100 #> # Era: Before Common Era (BCE): Gregorian years (365.2425 days), counted backwards from 1 yr_range(x) #> # CE years <yr[2]>: #> [1] 100 300 #> # Era: Common Era (CE): Gregorian years (365.2425 days), counted forwards from 0
Essentially these are all wrappers for base functions (sort(), min(), max() and range()) that are aware of the directionality of the era system attached to the vector: “CE” years are counted forwards, “BCE” years are counted backwards, etc.
I decided to implement them as prefixed functions instead of S3 methods for yr vectors because I didn’t want to suprise people when they used e.g. max() expecting the numerical maximum and got the chronologically latest value instead.