A guide to using the httr2 R package for interacting with web APIs, with examples for the US National Weather Service and OpenWeatherMap APIs.

This document provides a practical guide to using the httr2 package in R for interacting with web APIs. It includes two detailed examples: one that demonstrates how to call the US National Weather Service (NWS) API to retrieve hourly weather forecasts, and another that shows how to use the OpenWeatherMap API to get current weather data for a specific city. The guide covers the entire process, from constructing the API request to performing the request and extracting the relevant data from the JSON response.

The httr2 package provides a pipeable API for working with web APIs.

Example 1: call US weather API

Code

pak::pkg_install('httr2')

https://api.weather.gov/points/38.8894,-77.0352

Code

library(httr2)
library(tidyverse)

API link

Code

NWS_base_url <- 'https://api.weather.gov'

NWS_response_link <- request(NWS_base_url) |> 
  req_url_path_append(
    'points',
    '38.8894,-77.0352'
  ) 

NWS_response_link

create response and check connection

Code

NWS_response=NWS_response_link|> req_perform()
NWS_response

get forecast hourly url from response

Code

NWS_response |> 
  resp_body_json() |> 
  glimpse()

Code

forecast_url <- NWS_response |> 
  resp_body_json() |> 
  pluck('properties', 'forecastHourly')

forecast_url

make forecast hourly response

Code

forecast_response <- request(forecast_url) |> 
  req_perform()

forecast_response |> 
  resp_body_json() |> 
  glimpse()

get forecast hourly data

Code

extracted_data <- forecast_response |> 
  resp_body_json() |> 
  pluck('properties', 'periods') |> 
  map_dfr( # iterates over each list and binds rows to a tibble
    \(x) {
      tibble(
        time = x |> pluck('startTime'),
        temp_F = x |> pluck('temperature'),
        rain_prob = x |> pluck('probabilityOfPrecipitation', 'value'),
        forecast = x |> pluck('shortForecast')
      )
    }
  )

extracted_data

Example 2 :openweathermap

https://home.openweathermap.org/

Code

pak::pkg_install('httr2')

Code

library(httr2)

create response

Code

library(keyring)
openweathermap_base_url <- 'https://api.openweathermap.org/data/2.5'

openweathermap_api_key=key_get("openweathermap_api_key")

city='Bangkok'

openweathermap_response_link <- request(openweathermap_base_url) |> 
  req_url_path_append(
    paste0('weather?q=',city,'&appid=',openweathermap_api_key,'&units=metric')
  ) 

openweathermap_response_link

Code

openweathermap_response=openweathermap_response_link|> req_perform()
openweathermap_response

get data from response

Code

openweathermap_response |> 
  resp_body_json() |> 
  glimpse()

Code

openweathermap_response |> 
  resp_body_json() |> 
  pluck('main', 'temp') 

a=openweathermap_response |> 
  resp_body_json() |> 
  pluck('weather') 

(a[[1]])$main

openweathermap_response |> 
  resp_body_json() |> 
  pluck('name') 

openweathermap_response |> 
  resp_body_json() |> 
  pluck('coord', 'lon') 

openweathermap_response |> 
  resp_body_json() |> 
  pluck('coord', 'lat')

London air_pollution:

http://api.openweathermap.org/data/2.5/air_pollution?lat=51.5085&lon=-0.1257&appid=625ae405e4f11b5b957af484b77fbd62

Reference

https://httr2.r-lib.org/

https://www.youtube.com/watch?v=8tilyqp4bZY

https://www.youtube.com/watch?v=hmtE4QGIOuk

https://openweathermap.org/current

--- title: "使用R httr2 调用API" subtitle: "Using R httr2 to call API" author: "Tony D" date: "2025-03-15" categories: - Tool - R execute: warning: false error: false eval: false image: 'logo.png' --- A guide to using the `httr2` R package for interacting with web APIs, with examples for the US National Weather Service and OpenWeatherMap APIs. This document provides a practical guide to using the `httr2` package in R for interacting with web APIs. It includes two detailed examples: one that demonstrates how to call the US National Weather Service (NWS) API to retrieve hourly weather forecasts, and another that shows how to use the OpenWeatherMap API to get current weather data for a specific city. The guide covers the entire process, from constructing the API request to performing the request and extracting the relevant data from the JSON response. The `httr2` package provides a pipeable API for working with web APIs. # Example 1: call US weather API ```{r} pak::pkg_install('httr2') ``` https://api.weather.gov/points/38.8894,-77.0352 ```{r} library(httr2) library(tidyverse) ``` ## API link ```{r} NWS_base_url <- 'https://api.weather.gov' NWS_response_link <- request(NWS_base_url) |> req_url_path_append( 'points', '38.8894,-77.0352' ) NWS_response_link ``` ## create response and check connection ```{r} NWS_response=NWS_response_link|> req_perform() NWS_response ``` ## get forecast hourly url from response ```{r} NWS_response |> resp_body_json() |> glimpse() ``` ```{r} forecast_url <- NWS_response |> resp_body_json() |> pluck('properties', 'forecastHourly') forecast_url ``` ## make forecast hourly response ```{r} forecast_response <- request(forecast_url) |> req_perform() forecast_response |> resp_body_json() |> glimpse() ``` ## get forecast hourly data ```{r} extracted_data <- forecast_response |> resp_body_json() |> pluck('properties', 'periods') |> map_dfr( # iterates over each list and binds rows to a tibble \(x) { tibble( time = x |> pluck('startTime'), temp_F = x |> pluck('temperature'), rain_prob = x |> pluck('probabilityOfPrecipitation', 'value'), forecast = x |> pluck('shortForecast') ) } ) extracted_data ``` # Example 2 :openweathermap https://home.openweathermap.org/ ```{r} pak::pkg_install('httr2') ``` ```{r} library(httr2) ``` ## create response ```{r} library(keyring) openweathermap_base_url <- 'https://api.openweathermap.org/data/2.5' openweathermap_api_key=key_get("openweathermap_api_key") city='Bangkok' openweathermap_response_link <- request(openweathermap_base_url) |> req_url_path_append( paste0('weather?q=',city,'&appid=',openweathermap_api_key,'&units=metric') ) openweathermap_response_link ``` ```{r} openweathermap_response=openweathermap_response_link|> req_perform() openweathermap_response ``` ## get data from response ```{r} openweathermap_response |> resp_body_json() |> glimpse() ``` ```{r} openweathermap_response |> resp_body_json() |> pluck('main', 'temp') a=openweathermap_response |> resp_body_json() |> pluck('weather') (a[[1]])$main openweathermap_response |> resp_body_json() |> pluck('name') openweathermap_response |> resp_body_json() |> pluck('coord', 'lon') openweathermap_response |> resp_body_json() |> pluck('coord', 'lat') ``` London air_pollution: http://api.openweathermap.org/data/2.5/air_pollution?lat=51.5085&lon=-0.1257&appid=625ae405e4f11b5b957af484b77fbd62 # Reference https://httr2.r-lib.org/ https://www.youtube.com/watch?v=8tilyqp4bZY https://www.youtube.com/watch?v=hmtE4QGIOuk https://openweathermap.org/current