Chapter 17 Commuting time

do_eval=file.exists("commute_times.csv")

Commuting time is often mentioned as a valid reason for leaving one employer for another.

You are asked to calculate the commuting time for the employee working at your company. You decide that hyphotetically they must all arrive in the office at 8.30 am. In the Google you identified that there is google api for doing this, called Distance Matrix API, which works for a matrix of origins and destinations.

The information returned is based on the recommended route between start and end points and consists of rows containing duration and distance values for each pair." To use the Distance Matrix API, you must first activate the API in the Google Cloud Platform Console and obtain the proper authentication credentials. You need to provide your own API key in each request.

The documentation on how to do this is located here: https://developers.google.com/maps/documentation/distance-matrix/intro

A file with 200 fake names and addresses has been put together for you. The task is to add the commuting time next to each staff member. Normally google will charge us one dollar for checking 200 commuting times.

Please note that the departure_time specifies the desired time of departure must be in POSIXct. format and must be in the future (i.e.greater than sys.time()). If no value is specified it defaults to Sys.time().

Please note you can only specify one of arrival_time or departure_time, not both. If both are supplied, departure_time will be used.

library(googleway)
library(tidyverse)
library(lubridate)

# Set up here your api key key=
key = 'AIzaSyCOly69PDrlPlM42I378p2lmvNs8I2w'

d <- dmy_hms("10/09/2018 08:30")

arrival <- as.numeric(d)


from <- c("SE3+8UQ,UK")
to <- c("E14+5EU,UK")

test <- google_distance(origins = from,
                        destinations = to,
                        mode = "walking",
                        arrival_time = as.POSIXct(arrival, origin = "1970-01-01", tz = "UTC"),
                        key=key)

test$rows$elements[[1]]$distance

NULL

To make all this simpler, we put together an R function which can be used to analyse many results. Note this calls all modes of transport for every employee making it more costly than just running one mode per employee.

#' Get distance data between two points based on all the travel mode options. Works for many origin points.
#'
#' @param x A vector of origins in address or postcode format
#' @param dest A single destinationin address or postocde format
#' @param arrival_time A POSIXct datetime that folks need to arrive by
#' @param key A google distance API key
#' @param ... Additional options to pass to `google_distance()`
#'
#' @return Data.frame containing (typically) 4 rows per input element

google_distance_all =  function(x, dest, arrival_time, key, ...){
  
  # simple hygeine stuff
  gd = purrr::possibly(
    memoise::memoise(
      google_distance)
    , "Fail"
  )
  
  # Prep dataset
   interested_in = expand.grid(from=x, 
     mode=c("driving", "walking", "bicycling", "transit"), 
      stringsAsFactors = FALSE)
   # Perform google_distance calls for all combos
  purrr::map2(interested_in$from,interested_in$mode, 
     ~gd(.x, dest, mode=.y,
                        arrival_time = arrival_time,
                        key=key)
  ) %>% 
    # Extract relevant section
    purrr::map("rows") %>% 
    purrr::map("elements") %>% 
    purrr::flatten() %>% 
    # Simplify the data.frames
    purrr::map(unclass) %>% 
    purrr::map_df(purrr::flatten) %>% 
    # Add original lookup values
    cbind(interested_in)
}

This needs some packages installed to work

if(!require(purrr)) install.packages("purrr")
if(!require(memoise)) install.packages("memoise")
if(!require(googleway)) install.packages("googleway")

We need some information about our google API account, where our office is, and when we’re testing commute times for.

office = "E14 5EU"
monday_9am = as.POSIXct("2018-12-03 09:00")

Then we can use this function to get data for our 200 employees

the_200 <- read_csv("https://hranalytics.netlify.com/data/200_staff_members.csv")

results = google_distance_all(
  the_200$Postcode,
  office,
  arrival_time = monday_9am,
  key = key
)

write_csv(results, file.path("data"), "commute_times.csv")

results

# A tibble: 800 x 5
   text    value status from     mode   
   <chr>   <dbl> <chr>  <chr>    <chr>  
 1 16 mins   963 OK     E15 1NS  driving
 2 57 mins  3396 OK     W12 8ET  driving
 3 41 mins  2469 OK     SW1V 1AP driving
 4 19 mins  1123 OK     SE1 2RE  driving
 5 37 mins  2206 OK     WC1A 2QS driving
 6 43 mins  2604 OK     N6 5JW   driving
 7 31 mins  1871 OK     EC1N 8PN driving
 8 36 mins  2158 OK     WC2B 6TE driving
 9 31 mins  1841 OK     N1 9AZ   driving
10 24 mins  1423 OK     WC2R 3LD driving
# ... with 790 more rows

Now that we have this data we can answer questions about our employee’s commute times.

Who has the longest commutes by car?

results %>% 
  filter(mode == "driving") %>% 
  mutate(hours=value/60^2) %>% 
  top_n(10, hours) %>% 
  arrange(desc(hours))

# A tibble: 10 x 6
   text             value status from     mode       hours
   <chr>            <dbl> <chr>  <chr>    <chr>      <dbl>
 1 10 hours 46 mins 38745 OK     BT49 0BX driving 10.7625 
 2 10 hours 33 mins 37986 OK     BT51 3SQ driving 10.5517 
 3 6 hours 45 mins  24274 OK     G4 0JY   driving  6.74278
 4 5 hours 19 mins  19145 OK     CA1 1BG  driving  5.31806
 5 4 hours 35 mins  16519 OK     PL1 4GP  driving  4.58861
 6 4 hours 17 mins  15411 OK     BB5 3EZ  driving  4.28083
 7 3 hours 57 mins  14239 OK     OL10 2TL driving  3.95528
 8 3 hours 30 mins  12585 OK     LS23 7BA driving  3.49583
 9 3 hours 26 mins  12341 OK     LS24 9QW driving  3.42806
10 3 hours 18 mins  11882 OK     S10 3TR  driving  3.30056

We can look at the distributions overall too.

results %>% 
  mutate(hours=value/60^2) %>% 
  ggplot() +
  aes(x=hours) +
  geom_density() +
  scale_x_log10() +
  facet_wrap(~mode) +
  theme_minimal()