How to loop dataframe in R - r

Question

I want to get data from IMF.However the API data is limited
Therefor I get the data by continent.
How to loop the dateframe? (The data can get from "Before loop part",load data from api)
The reference cannot work.https://stackoverflow.com/questions/25284539/loop-over-a-string-variable-in-r
Before the loop
library(imfr)
library(countrycode)
data(codelist)
country_set <- codelist
country_set<- country_set %>%
select(country.name.en , iso2c, iso3c, imf, continent, region) %>% filter(!is.na(imf) & !is.na(iso2c))
africa_iso2<- country_set$iso2c[country_set$continent=="Africa"]
asia_iso2<- country_set$iso2c[country_set$continent=="Asia"]
americas_iso2<- country_set$iso2c[country_set$continent=="Americas"]
europe_iso2<- country_set$iso2c[country_set$continent=="Europe"]
oceania_iso2<- country_set$iso2c[country_set$continent=="Oceania"]
loop part
continent <- c("africa", "asia", "americas","europe","oceania")
for(i in 1:length(continent)){
var <- paste0("gdp_nsa_xdc_", continent[i])
var1 <- paste0(continent[i],"_iso2")
[[var]]<- imf_data(database_id = "IFS" , indicator = c("NGDP_NSA_XDC"),country =[[var1]],start = 2010, end = 2022,return_raw = TRUE)
[[var]]<- [[var]]$CompactData$DataSet$Series
}
data sample is
list(CompactData = list(`#xmlns:xsi` = "http://www.w3.org/2001/XMLSchema-instance",
`#xmlns:xsd` = "http://www.w3.org/2001/XMLSchema", `#xsi:schemaLocation` = "http://www.SDMX.org/resources/SDMXML/schemas/v2_0/message https://registry.sdmx.org/schemas/v2_0/SDMXMessage.xsd http://dataservices.imf.org/compact/IFS http://dataservices.imf.org/compact/IFS.xsd",
`#xmlns` = "http://www.SDMX.org/resources/SDMXML/schemas/v2_0/message",
Header = list(ID = "18e0aeae-09ec-4dfe-ab72-60aa16aaea84",
Test = "false", Prepared = "2022-10-19T12:02:28", Sender = list(
`#id` = "1C0", Name = list(`#xml:lang` = "en", `#text` = "IMF"),
Contact = list(URI = "http://www.imf.org", Telephone = "+ 1 [phone]")),
Receiver = list(`#id` = "ZZZ"), DataSetID = "IFS"), DataSet = list(
`#xmlns` = "http://dataservices.imf.org/compact/IFS",
Series = list(`#FREQ` = "Q", `#REF_AREA` = "US", `#INDICATOR` = "NGDP_NSA_XDC",
`#UNIT_MULT` = "6", `#TIME_FORMAT` = "P3M", Obs = structure(list(
`#TIME_PERIOD` = c("2020-Q1", "2020-Q2", "2020-Q3",
"2020-Q4", "2021-Q1", "2021-Q2", "2021-Q3", "2021-Q4",
"2022-Q1", "2022-Q2"), `#OBS_VALUE` = c("5254152",
"4930197", "5349433", "5539370", "5444406", "5784816",
"5883177", "6203369", "6010733", "6352982")), class = "data.frame", row.names = c(NA,
10L))))))

Answer 1

I suggest you create a list first, to which you will assign the value you want your loop to create. The following code creates a named list, and then at the end of the loop, assigns the value of each iteration to that named list:
continent <-
sapply(c("africa", "asia", "americas","europe","oceania"),
c, simplify = FALSE, USE.NAMES = TRUE)
for(i in seq_len(length(continent))) {
var <- paste0("gdp_nsa_xdc_", continent[i])
var1 <- get(paste0(continent[i],"_iso2"))
var <- imf_data(database_id = "IFS" , indicator = c("NGDP_NSA_XDC"),
country = var1, start = 2010, end = 2022,
return_raw = TRUE)
continent[[i]] <- var$CompactData$DataSet$Series
}
I don't necessarily understand the double brackets around [[var]]. Let me know if my answer does not correspond to what you were looking for!

Answer 2

We could use assign to create objects in the global env
for(i in 1:length(continent)){
var <- paste0("gdp_nsa_xdc_", continent[i])
var1 <- paste0(continent[i],"_iso2")
assign(var, imf_data(database_id = "IFS" , indicator = c("NGDP_NSA_XDC"),country =[[var1]],start = 2010, end = 2022,
return_raw = TRUE))
assign(var, get(var)$CompactData$DataSet$Series)
}