calendar

The goal of calendar is to make it easy to create, read, write, and work with iCalander (.ics, .ical or similar) files, and the scheduling data they represent, in R. iCalendar is an open standard for “exchanging calendar and scheduling information between users and computers” described at icalendar.org (the full spec can be found in a plain text file here).

Recently the UK Government endorsed the iCal format in a publication for the ‘Open Standards for Government’ series. An example .ics file is provided by the .gov.uk domain, which shows holidays in England and Wales.

Installation

install.packages("calendar")

Or install the cutting edge from GitHub

devtools::install_github("ATFutures/calendar")

library(calendar)

Example

A minimal example representing the contents of an iCalendar file is provided in the dataset ical_example, which is loaded when the package is attached. This is what iCal files look like:

ical_example
#>  [1] "BEGIN:VCALENDAR"                                  
#>  [2] "PRODID:-//Google Inc//Google Calendar 70.9054//EN"
#>  [3] "VERSION:2.0"                                      
#>  [4] "CALSCALE:GREGORIAN"                               
#>  [5] "METHOD:PUBLISH"                                   
#>  [6] "X-WR-CALNAME:atf-test"                            
#>  [7] "X-WR-TIMEZONE:Europe/London"                      
#>  [8] "BEGIN:VEVENT"                                     
#>  [9] "DTSTART:20180809T160000Z"                         
#> [10] "DTEND:20180809T163000Z"                           
#> [11] "DTSTAMP:20180810T094100Z"                         
#> [12] "UID:1119ejg4vug5758527atjcrqj3@google.com"        
#> [13] "CREATED:20180807T133712Z"                         
#> [14] "DESCRIPTION:\\n"                                  
#> [15] "LAST-MODIFIED:20180807T133712Z"                   
#> [16] "LOCATION:"                                        
#> [17] "SEQUENCE:0"                                       
#> [18] "STATUS:CONFIRMED"                                 
#> [19] "SUMMARY:ical programming mission"                 
#> [20] "TRANSP:OPAQUE"                                    
#> [21] "END:VEVENT"                                       
#> [22] "END:VCALENDAR"

Relevant fields can be found and extracted as follows:

which(ic_find(ical_example, "TSTAMP"))
#> [1] 11
ic_extract(ical_example, "TSTAMP")
#> [1] "D20180810T094100Z"

A larger example shows all national holidays in England and Wales. It can be read-in as follows:

ics_file <- system.file("extdata", "england-and-wales.ics", package = "calendar")
ics_raw = readLines(ics_file) 
head(ics_raw) # check it's in the ICS format
#> [1] "BEGIN:VCALENDAR"                     
#> [2] "VERSION:2.0"                         
#> [3] "METHOD:PUBLISH"                      
#> [4] "PRODID:-//uk.gov/GOVUK calendars//EN"
#> [5] "CALSCALE:GREGORIAN"                  
#> [6] "BEGIN:VEVENT"

A list representation of the calendar can be created using ic_list() as follows:

ics_list = ic_list(ics_raw)
ics_list[1:2]
#> [[1]]
#> [1] "DTEND;VALUE=DATE:20120103"                    
#> [2] "DTSTART;VALUE=DATE:20120102"                  
#> [3] "SUMMARY:New Year’s Day"                       
#> [4] "UID:ca6af7456b0088abad9a69f9f620f5ac-0@gov.uk"
#> [5] "SEQUENCE:0"                                   
#> [6] "DTSTAMP:20180806T114130Z"                     
#> 
#> [[2]]
#> [1] "DTEND;VALUE=DATE:20120407"                    
#> [2] "DTSTART;VALUE=DATE:20120406"                  
#> [3] "SUMMARY:Good Friday"                          
#> [4] "UID:ca6af7456b0088abad9a69f9f620f5ac-1@gov.uk"
#> [5] "SEQUENCE:0"                                   
#> [6] "DTSTAMP:20180806T114130Z"

A data frame representing the calendar can be created as follows (work in progress):

ics_df = ic_read(ics_file) # read it in
head(ics_df) # check the results
#> # A tibble: 6 × 6
#>   `DTEND;VALUE=DATE` `DTSTART;VALUE=DATE` SUMMARY         UID   SEQUENCE DTSTAMP
#>   <date>             <date>               <chr>           <chr> <chr>    <chr>  
#> 1 2012-01-03         2012-01-02           New Year’s Day  ca6a… 0        201808…
#> 2 2012-04-07         2012-04-06           Good Friday     ca6a… 0        201808…
#> 3 2012-04-10         2012-04-09           Easter Monday   ca6a… 0        201808…
#> 4 2012-05-08         2012-05-07           Early May bank… ca6a… 0        201808…
#> 5 2012-06-05         2012-06-04           Spring bank ho… ca6a… 0        201808…
#> 6 2012-06-06         2012-06-05           Queen’s Diamon… ca6a… 0        201808…

What class is each column?

vapply(ics_df, class, character(1))
#>   DTEND;VALUE=DATE DTSTART;VALUE=DATE            SUMMARY                UID 
#>             "Date"             "Date"        "character"        "character" 
#>           SEQUENCE            DTSTAMP 
#>        "character"        "character"

Trying on calendars ‘in the wild’

To make the package robust we test on a wide range of ical formats. Here’s an example from my work calendar, for example:

my_cal = ic_dataframe(ical_outlook)
my_cal$SUMMARY[1]
#> [1] "In Budapest for European R Users Meeting (eRum) conference"
# calculate the duration of the European R users meeting event:
my_cal$`DTEND;VALUE=DATE`[1] - my_cal$`DTSTART;VALUE=DATE`[1]
#> Time difference of 4 days

Related projects

• A Python package for working with ics files: https://github.com/ics-py/ics-py
• A JavaScript package by Mozilla: https://github.com/kewisch/ical.js
• Ruby library: https://github.com/icalendar/icalendar
• The ical R package on CRAN for reading .ics files: https://github.com/petermeissner/ical