R script om te demonstreren hoe je WFS paging kunt implementeren in R

verblijfsobjecten_in_zuidhorn.R

library(sf)
library(tmap)
library(magrittr)
library(httr)
library(xml2)

url <- parse_url("geodata.nationaalgeoregister.nl/bag/wfs?")
url$scheme <- "https"

# Request server limit
url$query <- list(service = "wfs", 
                  version = "2.0.0", 
                  request = "GetCapabilities")
server_limit <- build_url(url) %>% GET() %>% content(as = "text", encoding="UTF-8") %>% read_xml() %>% 
                xml_find_first("//ows:Constraint[@name='CountDefault']/ows:DefaultValue") %>% xml_integer()

# Request number of hits - verblijfobjecten in Zuidhorn
url$query <- list(service = "wfs", 
                  version = "2.0.0", 
                  request = "GetFeature",
                  typename = "bag:verblijfsobject",
                  cql_filter = "woonplaats = 'Zuidhorn'",
                  outputFormat = NULL,
                  resultType = "hits")
hits <- build_url(url) %>% GET() %>% content(as = "text", encoding="UTF-8") %>% read_xml() %>%
                           xml_find_first("//@numberMatched") %>% xml_integer()

# Request verblijfsobjecten in Zuidhorn using paging
url$query <- list(service = "wfs", 
                  version = "2.0.0", 
                  request = "GetFeature",
                  typename = "bag:verblijfsobject",
                  cql_filter = "woonplaats = 'Zuidhorn'",
                  outputFormat = "application/json",
                  resultType = "results",
                  sortBy = "bag:identificatie")
zuidhorn <- lapply(seq(0, hits, server_limit), function(x) {
    url$query$startindex <- x
    build_url(url) %>% st_read(stringsAsFactors = F)
}) %>% do.call(rbind, .)

nrow(zuidhorn)
qtm(zuidhorn)