R: Loop to capture weather data from multiple station - r

Question

I wanted to perform loop to capture weather data from multiple stations using code below:
library(rwunderground)
sample_df <- data.frame(airportid = c("K6A2",
"KAPA",
"KASD",
"KATL",
"KBKF",
"KBKF",
"KCCO",
"KDEN",
"KFFC",
"KFRG"),
stringsAsFactors = FALSE)
history_range(set_location(airport_code =sample_df$airportid), date_start = "20170815", date_end = "20170822",
limit = 10, no_api = FALSE, use_metric = FALSE, key = get_api_key(),
raw = FALSE, message = TRUE)
It won't work.

Answer 1

Currently, you are passing the entire vector (multiple character values) into the history_range call. Simply lapply to iteratively pass the vector values and even return a list of history_range() return objects. Below uses a defined function to pass the parameter. Extend the function as needed to perform other operations.
capture_weather_data <- function(airport_id) {
data <- history_range(set_location(airport_code=airport_id),
date_start = "20170815", date_end = "20170822",
limit = 10, no_api = FALSE, use_metric = FALSE, key = get_api_key(),
raw = FALSE, message = TRUE)
write.csv(data, paste0("/path/to/output/", airport_id, ".csv"))
return(data)
}
data_list <- lapply(sample_df$airportid, capture_weather_data)
Also, name each item in list to the corresponding airport_id character value:
data_list <- setNames(data_list, sample_df$airportid)
data_list$K6A2 # 1st ITEM
data_list$KAPA # 2nd ITEM
data_list$KASD # 3rd ITEM
...
In fact, with sapply (the wrapper to lapply) you can generate list and name each item in same call but the input vector must be a character type (not factor):
data_list <- sapply(as.character(sample_df$airportid), capture_weather_data,
simplify=FALSE, USE.NAMES=TRUE)
names(data_list)

Answer 2

I think this history_range function that you brought up, from the rwunderground package as I understand, requires a weather underground API key. I went to the site and even signed up for it, but the email validation process in order to get a key (https://www.wunderground.com/weather/api) doesn't seem to be working correctly at the moment.
Instead I went to the CRAN mirror (https://github.com/cran/rwunderground/blob/master/R/history.R) and from what I understand, the function accepts only one string as set_location argument. The example provided in the documentation is
history(set_location(airport_code = "SEA"), "20130101")
So what you should be doing as a "loop", instead, is
sample_df <- as.vector(sample_df)
for(i in 1:length(sample_df)){
history_range(
set_location(airport_code = sample_df[[i]]),
date_start = "20170815", date_end = "20170822",
limit = 10, no_api = FALSE, use_metric = FALSE,
key = get_api_key(),
raw = FALSE, message = TRUE)
}
If this doesn't work, let me know. (Ack, somebody also gave another answer to this question while I was typing this up.)