add_greatcircle: Add greatcircle
In mapdeck: Interactive Maps Using 'Mapbox GL JS' and 'Deck.gl'

Description Usage Arguments Details legend id Examples

Renders flat arcs along the great circle joining pairs of source and target points, specified as longitude/latitude coordinates.

add_greatcircle(
  map,
  data = get_map_data(map),
  layer_id = NULL,
  origin,
  destination,
  id = NULL,
  stroke_from = NULL,
  stroke_from_opacity = NULL,
  stroke_to = NULL,
  stroke_to_opacity = NULL,
  stroke_width = NULL,
  wrap_longitude = FALSE,
  tooltip = NULL,
  auto_highlight = FALSE,
  highlight_colour = "#AAFFFFFF",
  legend = F,
  legend_options = NULL,
  legend_format = NULL,
  palette = "viridis",
  na_colour = "#808080FF",
  update_view = TRUE,
  focus_layer = FALSE,
  transitions = NULL,
  digits = 6
)

`map`	a mapdeck map object
`data`	data to be used in the layer. All coordinates are expected to be EPSG:4326 (WGS 84) coordinate system
`layer_id`	single value specifying an id for the layer. Use this value to distinguish between shape layers of the same type. Layers with the same id are likely to conflict and not plot correctly
`origin`	vector of longitude and latitude columns, and optionally an elevation column, or an `sfc` column
`destination`	vector of longitude and latitude columns, and optionally an elevatino column, or an `sfc` column
`id`	an id value in `data` to identify layers when interacting in Shiny apps.
`stroke_from`	column of `data` or hex colour to use as the staring stroke colour. IIf using a hex colour, use either a single value, or a column of hex colours on `data`
`stroke_from_opacity`	Either a string specifying the column of `data` containing the stroke opacity of each shape, or a value between 1 and 255 to be applied to all the shapes. If a hex-string is used as the colour, this argument is ignored and you should include the alpha on the hex string
`stroke_to`	column of `data` or hex colour to use as the ending stroke colour. If using a hex colour, use either a single value, or a column of hex colours on `data`
`stroke_to_opacity`	Either a string specifying the column of `data` containing the stroke opacity of each shape, or a value between 1 and 255 to be applied to all the shapes. If a hex-string is used as the colour, this argument is ignored and you should include the alpha on the hex string
`stroke_width`	width of the stroke in pixels
`wrap_longitude`	logical, whether to automatically wrap longitudes over the 180th antimeridian.
`tooltip`	variable of `data` containing text or HTML to render as a tooltip
`auto_highlight`	logical indicating if the shape under the mouse should auto-highlight
`highlight_colour`	hex string colour to use for highlighting. Must contain the alpha component.
`legend`	either a logical indiciating if the legend(s) should be displayed, or a named list indicating which colour attributes should be included in the legend.
`legend_options`	A list of options for controlling the legend.
`legend_format`	A list containing functions to apply to legend values. See section legend
`palette`	string or matrix. String will be one of `colourvalues::colour_palettes()`. A matrix must have at least 5 rows, and 3 or 4 columns of values between [0, 255], where the 4th column represents the alpha. You can use a named list to specify a different palette for different colour options (where available), e.g. list(fill_colour = "viridis", stroke_colour = "inferno")
`na_colour`	hex string colour to use for NA values
`update_view`	logical indicating if the map should update the bounds to include this layer
`focus_layer`	logical indicating if the map should update the bounds to only include this layer
`transitions`	list specifying the duration of transitions.
`digits`	number of digits for rounding coordinates

add_greatcircle supports POINT sf objects

MULTIPOINT objects will be treated as single points. That is, if an sf objet has one row with a MULTIPOINT object consisting of two points, this will be expanded to two rows of single POINTs. Therefore, if the origin is a MULTIPOINT of two points, and the destination is a single POINT, the code will error as there will be an uneven number of rows

The legend_options can be used to control the appearance of the legend. This should be a named list, where the names are one of

css - a string of valid css for controlling the appearance of the legend
title - a string to use for the title of the legend
digits - number to round the legend values to

If the layer allows different fill and stroke colours, you can use different options for each. See examples in add_arc.

The legend_format can be used to control the format of the values in the legend. This should be a named list, where the names are one of

fill_colour
stroke_colour

depending on which type of colouring the layer supports.

The list elements must be functions to apply to the values in the legend.

The id is returned to your R session from an interactive shiny environment by observing layer clicks. This is useful for returning the data.frame row relating to the cliked shape.

From within a shiny server you would typically use observeEvent({input$map_arc_click}), where 'map' is the map_id supplied to mapdeckOutput(), and 'arc' is the layer you are clicking on

## You need a valid access token from Mapbox
set_token("MAPBOX_TOKEN")

url <- 'https://raw.githubusercontent.com/plotly/datasets/master/2011_february_aa_flight_paths.csv'
flights <- read.csv(url)
flights$id <- seq_len(nrow(flights))
flights$stroke <- sample(1:3, size = nrow(flights), replace = TRUE)
flights$info <- paste0("<b>",flights$airport1, " - ", flights$airport2, "</b>")

mapdeck( style = mapdeck_style("dark"), pitch = 45 ) %>%
  add_greatcircle(
  data = flights
  , layer_id = "greatcircle_layer"
  , origin = c("start_lon", "start_lat")
  , destination = c("end_lon", "end_lat")
  , stroke_from = "airport1"
  , stroke_to = "airport2"
  , stroke_width = "stroke"
  , tooltip = "info"
  , auto_highlight = TRUE
  , legend = TRUE
  , legend_options = list(
    stroke_from = list( title = "Origin airport" ),
    css = "max-height: 100px;")
 )

mapdeck( style = mapdeck_style("dark")) %>%
  add_greatcircle(
  data = flights
  , layer_id = "greatcircle_layer"
  , origin = c("start_lon", "start_lat")
  , destination = c("end_lon", "end_lat")
  , stroke_from = "airport1"
  , stroke_to = "airport2"
  , stroke_width = "stroke"
  )

## Using a 2-sfc-column sf object
library(sfheaders)

sf_flights <- sfheaders::sf_point( flights, x = "start_lon", y = "start_lat", keep = TRUE )
destination <- sfheaders::sfc_point( flights, x = "end_lon", y = "end_lat" )

sf_flights$destination <- destination

mapdeck() %>%
 add_greatcircle(
   data = sf_flights
   , origin = 'geometry'
   , destination = 'destination'
   , layer_id = 'greatcircles'
   , stroke_from = "airport1"
   , stroke_to = "airport2"
)