arc_read: Read an ArcGIS FeatureLayer, Table, or ImageServer

Description

arc_read() combines the functionality of arc_open() with arc_select() or arc_raster() to read an ArcGIS FeatureLayer, Table, or ImageServer to an sf or SpatRaster object. Optionally, set, check, or modify names for the returned data frame or sf object using the col_names and name_repair parameters. For ease of use and convenience, arc_read() allows users to access and query a FeatureLayer, Table, or ImageServer with a single function call instead of combining arc_open() and arc_select(). The conventions of col_select are based on functions for reading tabular data in the {readr} package.

Usage

arc_read(
  url,
  col_names = TRUE,
  col_select = NULL,
  n_max = Inf,
  name_repair = "unique",
  crs = NULL,
  ...,
  fields = NULL,
  alias = "drop",
  token = arc_token()
)

Value

An sf object, a data.frame, or an object of class SpatRaster.

Arguments

url

The url of the remote resource. Must be of length one.

col_names

Default TRUE. Column names or name handling rule. col_names can be TRUE, FALSE, NULL, or a character vector:

If TRUE, use existing default column names for the layer or table. If FALSE or NULL, column names will be generated automatically: X1, X2, X3 etc.
If col_names is a character vector, values replace the existing column names. col_names can't be length 0 or longer than the number of fields in the returned layer.

col_select

Default NULL. A character vector of the field names to be returned. By default, all fields are returned.

n_max

Defaults to Inf or an option set with options("arcgislayers.n_max" = <max records>). Maximum number of records to return.

name_repair

Default "unique". See vctrs::vec_as_names() for details. If name_repair = NULL and alias = "replace" may include invalid names.

crs

the spatial reference to be returned. If the CRS is different than the CRS for the input FeatureLayer, a transformation will occur server-side. Ignored if x is a Table.

...

Additional arguments passed to arc_select() if URL is a FeatureLayer or Table or arc_raster() if URL is an ImageLayer.

fields

Default NULL. a character vector of the field names to returned. By default all fields are returned. Ignored if col_names is supplied.

alias

Use of field alias values. Default c("drop", "label", "replace"),. There are three options:

"drop", field alias values are ignored.
"label": field alias values are assigned as a label attribute for each field.
"replace": field alias values replace existing column names. col_names

token

your authorization token.

Details

Examples

Run this code

if (FALSE) {
furl <- "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer/3"

# read entire service
arc_read(furl)

# apply tolower() to column names
arc_read(url, name_repair = tolower)

# use paste0 to prevent CRAN check NOTE
furl <- paste0(
  "https://sampleserver6.arcgisonline.com/arcgis/rest/services/",
  "EmergencyFacilities/FeatureServer/0"
)

# use field aliases as column names
arc_read(furl, alias = "replace")

# read an ImageServer directly
img_url <- "https://landsat2.arcgis.com/arcgis/rest/services/Landsat/MS/ImageServer"

arc_read(
  img_url,
  width = 100, height = 100,
  xmin = -71, ymin = 43,
  xmax = -67, ymax = 47.5,
  bbox_crs = 4326
)
}