Bus disruptions
Consider the Twitter data in the file translink.RData provided in the archive for this homework (you can load this using the R command load). Write an R function translink that takes 4 numerical arguments: a year (a numeric value such as 2020), a month (a numeric value between 1 and 12, inclusive with 1 indicating January), and a day of the month, and an hour of the day (in 24 hour time). The R function should return a list with two elements: 1) an element with the name start and with value specifying a character vector enumerating all bus routes that started to have disruptions during the hour indicated by the date and time provided to the function, 2) an element with the name stop and with value specifying a character vector enumerating all bus routes that stopped having disruptions during the hour indicated by the dat and time provided to the function. You don’t have to care about timezones for this question: you can assume that the time specified by the parameters to the function are in the same time zone as the data in translink.RData. Disruptions are defined as starting or stopping only if a Tweet indicating such is present in translink.RData (i.e., you don’t have to consider times that fall outside of the data provided in translink.RData). Note that some of the tweets in translink.RData may be truncated: you may ignore the truncated portions (this is approximate). Note that there are some corner cases among the tweets (not all of the disruptions are indicated with the same format). For full marks, consider some of the corner cases. Example usage is as follows:
> disruptions = translink(2020, 1, 26, 3)
> disruptions$start
[ 1 ] "401" "406"
> disruptions$stop
[1] "23"
