bcdata (version 0.5.0)

filter.bcdc_promise: Filter a query from bcdc_query_geodata()

Description

Filter a query from Web Feature Service using dplyr methods. This filtering is accomplished lazily so that the full sf object is not read into memory until collect() has been called.

See dplyr::filter for details.

Usage

# S3 method for bcdc_promise
filter(.data, ...)

Arguments

.data

object of class bcdc_promise (likely passed from bcdc_query_geodata())

...

Logical predicates with which to filter the results. Multiple conditions are combined with &. Only rows where the condition evaluates to TRUE are kept. Accepts normal R expressions as well as any of the special CQL geometry functions such as WITHIN() or INTERSECTS(). If you know CQL and want to write a CQL query directly, write it enclosed in quotes, wrapped in the CQL() function. e.g., CQL("ID = '42'").

If your filter expression contains calls that need to be executed locally, wrap them in local() to force evaluation in R before the request is sent to the server.

Methods (by class)

• filter(bcdc_promise): filter.bcdc_promise

Examples

# \donttest{
try(
  crd <- bcdc_query_geodata("regional-districts-legally-defined-administrative-areas-of-bc") %>%
    filter(ADMIN_AREA_NAME == "Cariboo Regional District") %>%
    collect()
)

try(
  ret1 <- bcdc_query_geodata("bc-wildfire-fire-perimeters-historical") %>%
    filter(FIRE_YEAR == 2000, FIRE_CAUSE == "Person", INTERSECTS(crd)) %>%
    collect()
)

# Use local() to force parts of your call to be evaluated in R:
try({
  # Create a bounding box around two points and use that to filter
  # the remote data set
  library(sf)
  two_points <- st_sfc(st_point(c(1164434, 368738)),
                     st_point(c(1203023, 412959)),
                     crs = 3005)

  # Wrapping the call to `st_bbox()` in `local()` ensures that it
  # is executed in R to make a bounding box that is then sent to
  # the server for the filtering operation:
  res <- bcdc_query_geodata("local-and-regional-greenspaces") %>%
    filter(BBOX(local(st_bbox(two_points, crs = st_crs(two_points))))) %>%
    collect()
})
# }