Skip to contents

Interactive leaflet map for classified rasters and transitions

Source: R/dft_map_interactive.R
dft_map_interactive.Rd

Build a toggleable leaflet map from classified SpatRasters or remote COG URLs served via titiler. Optionally overlay land cover transitions from dft_rast_transition(). Includes layer control, legend, and fullscreen.

Usage

dft_map_interactive(
  x,
  aoi = NULL,
  transition = NULL,
  class_table = NULL,
  source = "io-lulc",
  titiler_url = getOption("drift.titiler_url"),
  basemaps = c(Light = "CartoDB.Positron", `Esri Satellite` = "Esri.WorldImagery",
    `Google Satellite` = "https://mt1.google.com/vt/lyrs=s&x={x}&y={y}&z={z}",
    OpenTopoMap = "OpenTopoMap"),
  legend_position = "bottomright",
  zoom = 14
)

Arguments

x

A named list of classified terra::SpatRasters (e.g. from dft_rast_classify()) or a named character vector of COG URLs. A single SpatRaster or URL string is auto-wrapped into a length-1 list/vector. Names become the layer toggle labels (years, seasons, etc.).

aoi

An sf polygon for the area of interest outline. NULL (default) omits the AOI layer.

transition

Output of dft_rast_transition() — a list with elements raster (factor SpatRaster) and summary (tibble). Each transition type becomes a toggleable overlay. Stable transitions (same from/to class) are excluded by default. NULL (default) omits transition overlays.

class_table

A tibble with columns code, class_name, color (hex). When NULL, loaded via dft_class_table() using source.

source

Character. Used to load a shipped class table when class_table is NULL. One of "io-lulc" or "esa-worldcover".

titiler_url

Base URL of a titiler instance (e.g. "https://titiler.example.com"). Only used when x contains COG URLs. Defaults to getOption("drift.titiler_url"). If NULL in COG mode, an error is raised prompting the user to set the option.

basemaps

Named character vector of provider tile IDs or tile URL templates (starting with http). The first element is the default basemap. Names become radio button labels.

legend_position

Legend placement passed to leaflet::addLegend(). Set to NULL to suppress the legend.

zoom

Initial zoom level.

Value

A leaflet::leaflet htmlwidget. The first layer in x is visible by default; other layers are hidden but toggleable. Transition overlays are visible by default when supplied.

Details

When only x is supplied, classified layers appear as radio-toggle overlays (one visible at a time). When transition is also supplied, each transition type (e.g. Trees -> Rangeland) is added as a checkbox overlay that can be shown simultaneously on top of any classified layer.

Examples

# Single classified raster — returns a leaflet widget
r <- terra::rast(system.file("extdata", "example_2020.tif", package = "drift"))
classified <- dft_rast_classify(r, source = "io-lulc")
map <- dft_map_interactive(classified)
class(map)
#> [1] "leaflet"    "htmlwidget"

# Multiple years with AOI — toggle between time periods
aoi <- sf::st_read(
  system.file("extdata", "example_aoi.gpkg", package = "drift"),
  quiet = TRUE
)
files <- c("2017" = "example_2017.tif", "2020" = "example_2020.tif",
           "2023" = "example_2023.tif")
rasters <- lapply(files, function(f) {
  terra::rast(system.file("extdata", f, package = "drift"))
})
classified <- dft_rast_classify(rasters, source = "io-lulc")
map <- dft_map_interactive(classified, aoi = aoi)
if (interactive()) map

# Combined: classified layers + transition overlays
trans <- dft_rast_transition(classified, from = "2017", to = "2023",
                             from_class = "Trees")
map <- dft_map_interactive(classified, aoi = aoi, transition = trans)
if (interactive()) map

if (FALSE) { # \dontrun{
# Remote COGs via titiler (requires options(drift.titiler_url = "..."))
cogs <- c("2017" = "https://bucket.s3.amazonaws.com/lulc_2017.tif",
          "2023" = "https://bucket.s3.amazonaws.com/lulc_2023.tif")
dft_map_interactive(cogs, source = "io-lulc")
} # }