Layers represent represent a data service hosted by ArcGIS Online, ArcGIS Enterprise, Platform, or even an ArcGIS Hub site. Layers are how you will interact with your remotely hosted data.
The {arcgis} R metapackage is able to work with the most common types
of data services: feature services and image servers. The types of
layers that the R-ArcGIS Bridge does not yet support are vector and map
tile services.
Types of services
When working with these data services, each service type is assigned their own S3 class.
| Class | Description |
|---|---|
FeatureLayer |
Represents vector data. Can contain Point, MultiPoint, Polyline, or Polygon data |
Table |
A type of FeatureLayer in which there is no geometry present. Represents tabular data. |
ImageServer |
Provides access to raster imagery. |
FeatureServer |
A collection of FeatureLayer and Tables. |
GroupLayer |
A collection of FeatureLayer and Tables. |
MapServer |
A collection arbitrary data service types. |
Accessing data services
The R package {arcgislayers} provides access to services. Working with
data services follows a pattern:
- first, create a reference to a remote data service
- query the data service and bring the results back into R
Creating data service objects
Using {arcgislayers}, the function arc_open() will create a
reference to a service based on its url.
library(arcgis)
# feature service url
furl <- "https://services3.arcgis.com/ZvidGQkLaDJxRSJ2/arcgis/rest/services/PLACES_LocalData_for_BetterHealth/FeatureServer/4"
# feature layer
flayer <- arc_open(furl)
flayer#> <FeatureLayer>
#> Name: ZCTAs
#> Geometry Type: esriGeometryPolygon
#> CRS: 3785
#> Capabilities: Query,Extract
Querying feature services
To bring data from the service into memory in R, you must use
arc_select().
Always bring as little data as possible into memory. Utilize the
fields and where arguments.
arc_select(
flayer,
where = "TotalPopulation > 100000",
fields = c("objectid", "totalpopulation", "zcta5")
)#> Simple feature collection with 23 features and 3 fields
#> Geometry type: POLYGON
#> Dimension: XY
#> Bounding box: xmin: -13584740 ymin: 3464366 xmax: -8218961 ymax: 5130153
#> Projected CRS: WGS 84 / Pseudo-Mercator
#> First 10 features:
#> OBJECTID TotalPopulation ZCTA5
#> 1 2360 135256 08701
#> 2 2529 103660 10467
#> 3 2705 100330 11207
#> 4 2706 101958 11208
#> 5 2717 103447 11219
#> 6 2718 105797 11220
#> 7 2724 101727 11226
#> 8 2733 100687 11236
#> 9 2751 117110 11368
#> 10 2755 105712 11373
#> geometry
#> 1 POLYGON ((-8266867 4879637,...
#> 2 POLYGON ((-8225100 4995955,...
#> 3 POLYGON ((-8228297 4966147,...
#> 4 POLYGON ((-8225296 4965937,...
#> 5 POLYGON ((-8239056 4957776,...
#> 6 POLYGON ((-8241925 4958752,...
#> 7 POLYGON ((-8234030 4960513,...
#> 8 POLYGON ((-8228926 4961495,...
#> 9 POLYGON ((-8223473 4976473,...
#> 10 POLYGON ((-8225601 4975030,...