Trips

David Cooley

2020-08-17

The trips layer requires an sf object with XYZM dimension, where Z is elevation and M is a timestamp

In this example I’m taking the mapdeck::roads data, and assigning a random timestamp to each coordinate point in the lines.

The timestamps have to be positive, and in sequential order.

library(sf)
library(sfheaders)
library(data.table)

set_token( "MAPBOX_TOKEN" )
dt <- sfheaders::sf_to_df( mapdeck::roads )
setDT( dt )

dt[, elev := 0 ]
dt[, seq := 1:.N, by = linestring_id ]
dt1 <- dt[ seq == 1]
dt1[, start_time := sample(1:100, size = .N, replace = T)]
dt[
    dt1[, .(linestring_id, start_time)]
    , on = c("linestring_id")
    , start_time := i.start_time
    ]

dt[, time := start_time + seq ]
s <- dt[, min( time )]
e <- dt[, max( time )]

setorder( dt, linestring_id )
sfc <- sfheaders::sfc_linestring(
    obj = dt
    , x = "x"
    , y = "y"
    , z = "elev"
    , m = "time"
    , linestring_id = "linestring_id"
)

sf <- roads
sf$geometry <- sfc

mapdeck(
    location = c(145, -37.8)
    , zoom = 10
    , style = mapdeck_style("dark")
) %>%
    add_trips(
        data = sf
        , stroke_colour = "ROAD_NAME"
        , start_time = s
        , end_time = e
        , trail_length = 50
    )

Trips