Is there a way to automate extraction of elements from two or more lists?

Question

My goal is to automate fetching of trends data along with the extraction of "interest_over_time" from the lists.

Considering it a two-step problem:

• Automating fetching of data based on a group of keywords

• Extracting elements automatically in a methodical manner

I am not able to complete step 2.

Any ideas on how to get this done?

Step1 - Automating fetch of google trends data

library(gtrendsR)
a <- c("sony", "apple")

for (i in a) {
  name <- (paste(i, sep=""))
  assign(name, gtrends(keyword=i, time="now 1-H"))
  print(name)
}

Step2 - Extracting elements

sony[["interest_over_time"]]

instead of doing it like above manually, can I use for or some other function to automate this?

Answer 1

Here are a couple of ways that I think will give you what you want.

library(gtrendsR)

a = c("sony","apple")

First Way: using base R

gtrends_interest <- function(keyword) gtrends(keyword = keyword, time = "now 1-H")[["interest_over_time"]]
trends_data <- do.call('rbind', lapply(a, gtrends_interest))

Second Way: using purrr

library(purrr)
trends_data2 <- a %>%
  map_df( ~ gtrends(keyword = ., time = "now 1-H")[["interest_over_time"]])

Both methods will return a data.frame with the interest_over_time from each element in a stacked.

I prefer the second since map() becomes very powerful once you get a hang of it.