trip_purpose table code

[ashleyasmus]

RSG uses the following code to derive the trip purpose table. This is very similar to what is currently in metc.tbi.helper, but removes some 995s, -1s, etc. This code also has some logical checks (stopifnot() checks) to ensure the data run correctly.

## Derive Trip Purpose Table -----------------------------------------
 
dat_all_unified$trip[survey_year == 2019, linked_trip_id := 
                       ifelse(linked_trip_num < 100,
                              paste0(person_id, '0', linked_trip_num), 
                              paste0(person_id, linked_trip_num))]
 
linked_trips =
  dat_all_unified$trip[
    , .(
      # First origin
      o_purpose = first(o_purpose),
      # Last destination
      d_purpose = last(d_purpose),
      # trip weight:
      linked_trip_weight = first(trip_weight),
      # distance (total):
      distance = sum(distance_miles)
    ),
    keyby = .(linked_trip_id, person_id, hh_id, survey_year)
  ]
 
# get rid of change mode trips (origin)
linked_trips = linked_trips[!o_purpose %in% 58]
 
# get rid of change mode trips (destination)
linked_trips = linked_trips[!d_purpose %in% 58]
 
# Derive Non-Imputed Trip Purpose Table ========================================
 
## Split linked trips ----------------------------------------------------------
 
### ... 1 Home-based trips ----------------------
home_purpose = 1
 
# Home-based trips start or end at home
hb = copy(linked_trips)
 
hb = hb[(o_purpose == home_purpose |
           d_purpose == home_purpose)]
 
nrow(hb) / nrow(linked_trips)
# 56% of linked trips are home-based.
 
### ... 2 Non-home-based trips ----------------------
 
# Non-home-based trips neither start nor end at home:
nhb = copy(linked_trips)
nhb = nhb[!linked_trip_id %in%
            hb$linked_trip_id]
 
# Check that nhb trips do not start OR end at home:
stopifnot(nrow(nhb[o_purpose == home_purpose]) == 0)
stopifnot(nrow(nhb[d_purpose == home_purpose]) == 0)
 
 
# Check that the number of linked trips is equal to the categories into which we've split them:
stopifnot(nrow(hb) +  
            nrow(nhb) ==
            nrow(linked_trips))
 
## Assign trip purpose ---------------------------------------------------------
 
### ... 1 Home-based trips ----------------------------------------------------
 
# Home-Based trips get whatever the non-home-based end is:
hb[, purpose := fcase(
  o_purpose == home_purpose | o_purpose == 995 | o_purpose == -1, d_purpose,
  d_purpose == home_purpose | d_purpose == 995 | d_purpose == -1, o_purpose
)]
 
setnames(hb, 
         old = c('linked_trip_weight'),
         new = c('trip_purpose_weight'))
 
### ... 2 Non-home-based trips -------------------------------------------------
 
### ...... one valid end  ------------------------------------------------------
nhb_oneend = nhb[is.na(o_purpose) | is.na(d_purpose) | o_purpose == 995 | d_purpose == 995 | o_purpose == -1 | d_purpose == -1]
nrow(nhb_oneend) # 0
 
# for these single-ended non-home-based trips, assign the purpose to the non-missing end
nhb_oneend[, `:=` (
  purpose = fcase(
    is.na(o_purpose) | o_purpose == 995 | o_purpose == -1,
    d_purpose,
    is.na(d_purpose) | d_purpose == 995 | d_purpose == -1,
    o_purpose
  )
)]
 
setnames(nhb_oneend, 'linked_trip_weight', 'trip_purpose_weight')
 
### ...... two valid ends  -----------------------------------------------------
nhb_twoend = nhb[!is.na(o_purpose) & o_purpose != 995 & o_purpose != -1 &
                   !is.na(d_purpose) & d_purpose != 995 & d_purpose != -1]
 
# check - we've split nhb trips into two complete categories:
stopifnot(nrow(nhb) ==
            nrow(nhb_oneend) +
            nrow(nhb_twoend))
 
# Split into origin and destination:
nhb_twoend_o = copy(nhb_twoend)
nhb_twoend_o = nhb_twoend_o[, `:=` (purpose = o_purpose)]
 
nhb_twoend_d = copy(nhb_twoend)
nhb_twoend_d = nhb_twoend_d[, `:=` (purpose = d_purpose)]
 
# divide NHB trip weight in half:
nhb_twoend_o[, trip_purpose_weight := linked_trip_weight / 2]
nhb_twoend_o[, linked_trip_weight := NULL]
 
nhb_twoend_d[, trip_purpose_weight  := linked_trip_weight  / 2]
nhb_twoend_d[, linked_trip_weight := NULL]
 
 
### 3 Combine  -----------------------------------------------------
trip_purpose = rbindlist(list(hb,
                              nhb_oneend,
                              nhb_twoend_o,
                              nhb_twoend_d),
                         use.names = TRUE)
 
stopifnot(round(sum(
  linked_trips$linked_trip_weight, na.rm = T
)) ==
  round(sum(
    trip_purpose$trip_purpose_weight, na.rm = T
  )))
 
trip_purpose[, sum(trip_purpose_weight, na.rm = T), keyby = purpose]
 
nrow(trip_purpose) / nrow(linked_trips)
# Splitting into origin and destination for our two-ended, nhb trips increased
# the table size by 42%
 
# Mark these as two-ended trips:
trip_purpose[, num_trips_adj := ifelse(linked_trip_id %in% c(nhb_twoend$linked_trip_id), 0.5, 1)]
 
stopifnot(sum(trip_purpose$num_trips_adj) == nrow(linked_trips))
 
# Create trip purpose ID:
# make a sequential linked trip number
 
trip_purpose = trip_purpose[order(hh_id, person_id, linked_trip_id)]
trip_purpose[, trip_purpose_num := 1:.N,
             keyby = .(hh_id, person_id)]
 
# make a linked trip ID with this linked_trip_num
trip_purpose[, trip_purpose_id :=
               bit64::as.integer64(paste0(
                 person_id,
                 str_pad(
                   trip_purpose_num,
                   width = 3,
                   side = "left",
                   pad = "0"
                 )
               ))]
 
stopifnot(uniqueN(trip_purpose$trip_purpose_id) == nrow(trip_purpose))