openweather api to get multiple cities - r

Question

get_weather_forecaset_by_cities <- function(city_names){
df <- data.frame("weather_data_frame" )
for (city_name in city_names){
forecast_url <- 'https://api.openweathermap.org/data/2.5/forecast'
forecast_query <- list(q = city_name, appid = "a297d3b46d0b5a7aab6dde3512962b99", units="metric")
for(result in results) {
city <- c(city, city_name)
}
}
return(df)
}
Need help to understand the above given code, i am specifically stuck in the line 6 of the code, in the markdown it says "# Loop the json result" (Note: json_result is a list of lists).
But my actual task is this "Complete and call get_weather_forecaset_by_cities function with a list of cities, and write the data frame into a csv file called cities_weather_forecast.csv"
Which parts should i have to fill in and how?
cities <- c("Seoul", "Washington, D.C.", "Paris", "Suzhou")
cities_weather_df <- get_weather_forecaset_by_cities(cities)
After running the next line of codes it shows this error
"Error in get_weather_forecaset_by_cities(cities): object 'json_result' not found
Traceback:
get_weather_forecaset_by_cities(cities)"

Answer 1

Since this is a homework question, it's not appropriate to provide a complete answer. However, a function that receives a list of city names and obtains their 5 day weather forecasts from openweathermap.org looks like this:
get_weather_forecast_by_cities <- function(city_names){
library(dplyr)
library(tidyr)
library(jsonlite)
df <- NULL # initialize a data frame
for(c in city_names){
aForecast <- paste0("http://api.openweathermap.org/data/2.5/forecast?",
"q=",c,
"&appid=<your API KEY here>",
"&units=metric")
message(aForecast)
aCity <- fromJSON(aForecast)
# extract the date / time content and convert to POSIXct
# extract the periodic weather content, note that
# tidyr::unnest() is helpful here
# add the city name
# bind the results into the output data frame, df
}
df # return data frame
}
We replace the commented areas with code and run the function as follows:
source("./examples/get_weather_forecast_by_cities.R")
cityList <- c("Seoul","Paris","Chicago","Beijing","Suzhou")
theData <-get_weather_forecast_by_cities(cityList)
head(theData)
...and the first few rows of output:
> head(theData)
# A tibble: 6 × 24
dt temp feels_like temp_min temp_max pressure sea_level
<dttm> <dbl> <dbl> <dbl> <dbl> <int> <int>
1 2022-08-03 03:00:00 27.4 31.5 27.4 29.9 1011 1011
2 2022-08-03 06:00:00 29.4 34.2 29.4 31.0 1010 1010
3 2022-08-03 09:00:00 29.2 33.2 29.2 29.2 1009 1009
4 2022-08-03 12:00:00 26.9 29.9 26.9 26.9 1010 1010
5 2022-08-03 15:00:00 25.7 26.7 25.7 25.7 1010 1010
6 2022-08-03 18:00:00 25.0 26.1 25.0 25.0 1010 1010
# … with 17 more variables: grnd_level <int>, humidity <int>, temp_kf <dbl>,
# id <int>, main <chr>, description <chr>, icon <chr>, all <int>, speed <dbl>,
# deg <int>, gust <dbl>, visibility <int>, pop <dbl>, `3h` <dbl>, pod <chr>,
# dt_txt <chr>, city <chr>
>
At this point we have a data frame that can be easily written to csv with write.csv() which is left as an exercise for the reader.