Latent positions may be queried using arbitrary date-time values. The only method (for now) is 'linear', but default should be 'geodesic'. In time we include more methods to match the GeoPandas implementation.
track_query(x, y, date = NULL, query, type = "linear")longitude
latitude
date-time in POSIXct (or can be ignore, for relative index-time)
required argument, date-time values to return inferred x, y positions for
linear, geodesic, rhumb, forward, backward, nearest (also need open/closed intervals)
data frame of 'x,y,date' of inferred positions
If date is not included, time itself is treated as the obvious index on n-locations so
simple relative time, and query is expected to match this.
We use group_modify to keep the id groups:
trips0 %>% group_by(id) %>% group_modify(~track_query(.x$x, .x$y, query = c(4.5, 6.7)))
track_query(trips0$x[1:10], trips0$y[1:10], query = c(4.5, 5.5, 6.5))
#> Warning: date is null, so assuming linear relative movement in time
#> # A tibble: 3 × 3
#> x y date
#> <dbl> <dbl> <dbl>
#> 1 116. -42.0 4.5
#> 2 117. -41.9 5.5
#> 3 117. -41.8 6.5
track_query(trips0$x[1:10], trips0$y[1:10], trips0$date[1:10], query = trips0$date[1:10] + 10)
#> # A tibble: 10 × 3
#> x y date
#> <dbl> <dbl> <dttm>
#> 1 115. -42.4 2001-01-01 15:40:00
#> 2 116. -41.4 2001-01-01 18:17:02
#> 3 116. -41.1 2001-01-01 21:03:48
#> 4 117. -42.1 2001-01-01 22:09:51
#> 5 116. -41.9 2001-01-01 23:34:04
#> 6 118. -42.0 2001-01-02 01:25:22
#> 7 117. -41.7 2001-01-02 06:45:50
#> 8 118. -40.9 2001-01-02 10:01:36
#> 9 118. -39.7 2001-01-02 13:50:09
#> 10 NA NA 2001-01-02 16:24:56
s <- seq(min(trips0$date), max(trips0$date), by = "1 hour")