Declare a data source for a viewer spec — mgl

Two transport modes: * `type = "table"` (default) — a data.frame from R, serialized as Arrow IPC and registered in DuckDB-WASM under its name. Mosaic / deck.gl panels reference it by that name. * `type = "duckdb"` — a SQL query against the R-side DuckDB connection. Result is streamed as Arrow IPC (or GeoArrow IPC when `format = "geoarrow"`).

Usage

mgl_data(
  type = c("table", "duckdb"),
  df = NULL,
  query = NULL,
  format = c("arrow", "geoarrow", "json")
)

Arguments

type: `"table"` for an in-memory data.frame or `"duckdb"` for a SQL query against the `con` passed to [mosaic_gl()].
df: Data frame used when `type = "table"`.
query: SQL query used when `type = "duckdb"`.
format: Transport format for DuckDB queries. `"geoarrow"` will use a WKB polygon envelope for `cell_ID` + `geometry` result sets and otherwise falls back to Arrow IPC.

Value

A list describing the data source, for the `data` field of [mgl_spec()].

Examples

mgl_data(type = "table", df = data.frame(x = 1:3, y = 3:1))
#> $type
#> [1] "table"
#> 
#> $df
#>   x y
#> 1 1 3
#> 2 2 2
#> 3 3 1
#> 
mgl_data(type = "duckdb", query = "SELECT x, y FROM points")
#> $type
#> [1] "duckdb"
#> 
#> $query
#> [1] "SELECT x, y FROM points"
#> 
#> $format
#> [1] "arrow"
#>