问题
I'm working with the httr package in R in an attempt to query the postcode.io API (http://postcodes.io/docs).
I can successfully query a single postcode as per the instructions using:
sample4 <- GET("api.postcodes.io/postcodes/EN14RF")
When I try and query multiple postcodes I'm becoming a little unstuck. The postcode.io instructions suggest
POST https://api.postcodes.io/postcodes?q=[postcode]
where a JSON object containing an array of postcodes is specified. I have an R vector containing postcodes which I have attempted to convert to a JSON object as such with:
a <- toJSON(a)
where my R vector 'a' is:
structure(c(4L, 5L, 3L, 6L, 1L, 2L), .Label = c("Bn14 9aw", "CR0 4BE", "E5 8HB", "EN1 4RF", "G42 8QN", "SA1 3UL"), class = "factor")
Now when I try and query the API with the following line of code:
sample4 <- POST("https://api.postcodes.io/postcodes?q=[postcode]", body = list(postcode = add1JSON))
I get an error: "Invalid JSON submitted. You need to submit a JSON object with an array of postcodes or geolocation objects"
I have a feeling this is because I am not providing an array but an unnamed list e.g. my JSON object should look like this:
{"postcodes":"[ \"EN14RF\", \"G428QN\", \"E58HB\", \"SA13UL\", \"Bn149aw\", \"CR04BE\" ]"}
Not this: "[ \"EN14RF\", \"G428QN\", \"E58HB\", \"SA13UL\", \"Bn149aw\", \"CR04BE\" ]"
Can anyone help me with this? I've a feeling it is something to do with my toJSON call, but have been unable to find a similar example on the forum or on the API developers page:(
Many thanks
Marty
回答1:
They have very poorly written API docs. This seems to be the intent of this particular API call:
library(httr)
library(jsonlite)
library(dplyr)
post_codes <- c("Bn14 9aw", "CR0 4BE", "E5 8HB", "EN1 4RF", "G42 8QN", "SA1 3UL")
res <- POST("https://api.postcodes.io/postcodes",
body=list(postcodes=post_codes),
encode="json")
status_code(res)
## [1] 200
content(res, as="text") %>%
fromJSON(flatten=TRUE) %>%
glimpse()
## List of 2
## $ status: int 200
## $ result:'data.frame': 6 obs. of 29 variables:
## ..$ query : chr [1:6] "Bn14 9aw" "E5 8HB" "CR0 4BE" "EN1 4RF" ...
## ..$ result.postcode : chr [1:6] "BN14 9AW" "E5 8HB" "CR0 4BE" "EN1 4RF" ...
## ..$ result.quality : int [1:6] 1 1 1 1 1 1
## ..$ result.eastings : int [1:6] 514948 534934 531978 534957 264583 258092
## ..$ result.northings : int [1:6] 104386 185332 164963 199610 192273 662417
## ..$ result.country : chr [1:6] "England" "England" "England" "England" ...
## ..$ result.nhs_ha : chr [1:6] "South East Coast" "London" "London" "London" ...
## ..$ result.longitude : num [1:6] -0.3693 -0.0553 -0.1055 -0.0494 -3.9572 ...
## ..$ result.latitude : num [1:6] 50.8 51.6 51.4 51.7 51.6 ...
## ..$ result.parliamentary_constituency: chr [1:6] "East Worthing and Shoreham" "Hackney South and Shoreditch" "Croydon South" "Enfield North" ...
## ..$ result.european_electoral_region : chr [1:6] "South East" "London" "London" "London" ...
## ..$ result.primary_care_trust : chr [1:6] "West Sussex" "City and Hackney Teaching" "Croydon" "Enfield" ...
## ..$ result.region : chr [1:6] "South East" "London" "London" "London" ...
## ..$ result.lsoa : chr [1:6] "Worthing 008C" "Hackney 017B" "Croydon 024D" "Enfield 002E" ...
## ..$ result.msoa : chr [1:6] "Worthing 008" "Hackney 017" "Croydon 024" "Enfield 002" ...
## ..$ result.incode : chr [1:6] "9AW" "8HB" "4BE" "4RF" ...
## ..$ result.outcode : chr [1:6] "BN14" "E5" "CR0" "EN1" ...
## ..$ result.admin_district : chr [1:6] "Worthing" "Hackney" "Croydon" "Enfield" ...
## ..$ result.parish : chr [1:6] "Worthing, unparished area" "Hackney, unparished area" "Croydon, unparished area" "Enfield, unparished area" ...
## ..$ result.admin_county : chr [1:6] "West Sussex" NA NA NA ...
## ..$ result.admin_ward : chr [1:6] "Gaisford" "Homerton" "Waddon" "Turkey Street" ...
## ..$ result.ccg : chr [1:6] NA "NHS City and Hackney" "NHS Croydon" "NHS Enfield" ...
## ..$ result.nuts : chr [1:6] "West Sussex (South West)" "Hackney and Newham" "Croydon" "Enfield" ...
## ..$ result.codes.admin_district : chr [1:6] "E07000229" "E09000012" "E09000008" "E09000010" ...
## ..$ result.codes.admin_county : chr [1:6] "E10000032" "E99999999" "E99999999" "E99999999" ...
## ..$ result.codes.admin_ward : chr [1:6] "E05007698" "E05009376" "E05000167" "E05000211" ...
## ..$ result.codes.parish : chr [1:6] "E43000150" "E43000202" "E43000198" "E43000200" ...
## ..$ result.codes.ccg : chr [1:6] "E38000213" "E38000035" "E38000040" "E38000057" ...
## ..$ result.codes.nuts : chr [1:6] "UKJ27" "UKI41" "UKI62" "UKI54" ...
回答2:
According to the documentation of the httr package, you would need to set the encode parameter to json as follows:
url <- "https://api.postcodes.io/postcodes"
body <- list(a = 1, b = 2, c = 3)
# JSON encoded
r <- POST(url, body = body, encode = "json")
To see the actual request, you can use the verbose() parameter from an interactive console:
POST(url, body = body, encode = "json", verbose())
回答3:
You can put any JSON array into an R format that can pass through httr like this:
body <- fromJSON("{"postcodes":"[ \"EN14RF\", \"G428QN\", \"E58HB\", \"SA13UL\", \"Bn149aw\", \"CR04BE\" ]"}")
then post:
sample4 <- POST("https://api.postcodes.io/postcodes?q=[postcode]",
body = body,
encode = "json")
来源：https://stackoverflow.com/questions/38700871/httr-post-request-to-api-returns-400-error