无法将geojson/json文件读入R以便在地图上绘图 [英] Trouble reading in geojson/json file into R for plotting on map
问题描述
我正在尝试读取一个json文件,该文件包含R中的折线,以便在传单或ggmap中进行绘制.该文件为geojson格式.
I'm trying to read in a json file which contains polylines into R for plotting in leaflet or ggmap. The file is in the geojson format.
可以在以下位置找到文件: http://datasets.antwerpen.be/v4/gis/statistischesector.json
The file can be found at: http://datasets.antwerpen.be/v4/gis/statistischesector.json
我尝试过:
library(rgdal)
library(jsonlite)
library(leaflet)
geojson <- readLines("statistischesector.json", warn = FALSE) %>%
paste(collapse = "\n") %>%
fromJSON(simplifyVector = FALSE)
这实际上是从文件中读取的,但似乎格式错误,无法进行进一步处理.
This actually reads in the file but it seems to be in a wrong format for further processing.
或者:
readOGR(dsn="~/statistischesector.json", layer="OGRGeoJSON")
返回:
Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv, :
Cannot open data source
欢迎任何帮助!
推荐答案
这是一种方法
library("jsonlite")
library("leaflet")
x <- jsonlite::fromJSON("http://datasets.antwerpen.be/v4/gis/statistischesector.json", FALSE)
geoms <- lapply(x$data, function(z) {
dat <- tryCatch(jsonlite::fromJSON(z$geometry, FALSE), error = function(e) e)
if (!inherits(dat, "error")) {
list(type = "FeatureCollection",
features = list(
list(type = "Feature", properties = list(), geometry = dat)
))
}
})
leaflet() %>%
addTiles() %>%
addGeoJSON(geojson = geoms[1]) %>%
setView(
lng = mean(vapply(geoms[1][[1]]$features[[1]]$geometry$coordinates[[1]], "[[", 1, 1)),
lat = mean(vapply(geoms[1][[1]]$features[[1]]$geometry$coordinates[[1]], "[[", 1, 2)),
zoom = 12)
leaflet::addGeoJSON
确实确实需要特定的格式.例如,在 http://geojsonlint.com/上使用geojson字符串就可以了,但是需要对其进行调整才能使用leaflet
.另外,至少有一个格式错误的字符串,所以我添加了tryCatch
来跳过这些字符串
leaflet::addGeoJSON
does indeed want a particular format. E.g., the geojson strings are fine on http://geojsonlint.com/ but they need to be tweaked to work with leaflet
. also, there was at least one string that was malformed, so i added a tryCatch
to skip those
所有多边形
gg <- list(type = "FeatureCollection",
features =
Filter(Negate(is.null), lapply(x$data, function(z) {
dat <- tryCatch(jsonlite::fromJSON(z$geometry, FALSE), error = function(e) e)
if (!inherits(dat, "error")) {
list(type = "Feature",
properties = list(),
geometry = dat)
} else {
NULL
}
}))
)
leaflet() %>%
addTiles() %>%
addGeoJSON(geojson = gg) %>%
setView(lng = 4.5, lat = 51.3, zoom = 10)
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