loop within a loop for JSON files in R - json

Question

I am trying to aggregate a bunch of JSON files in to a single one for three sources and three years. While so far I have only been able to do it through the tedious way, I am sure I could do it in a smarter and more elegant manner.
json1 <- lapply(readLines("NYT_1989.json"), fromJSON)
json2 <- lapply(readLines("NYT_1990.json"), fromJSON)
json3 <- lapply(readLines("NYT_1991.json"), fromJSON)
json4 <- lapply(readLines("WP_1989.json"), fromJSON)
json5 <- lapply(readLines("WP_1990.json"), fromJSON)
json6 <- lapply(readLines("WP_1991.json"), fromJSON)
json7 <- lapply(readLines("USAT_1989.json"), fromJSON)
json8 <- lapply(readLines("USAT_1990.json"), fromJSON)
json9 <- lapply(readLines("USAT_1991.json"), fromJSON)
jsonl <- list(json1, json2, json3, json4, json5, json6, json7, json8, json9)
Note that the year period goes equally for the three files from 1989 to 1991. Any ideas? Thanks!
PS: Example of the data inside each file:
{"date": "December 31, 1989, Sunday, Late Edition - Final", "body": "Frigid temperatures across much of the United States this month sent demand for heating oil soaring, providing a final upward jolt to crude oil prices. Some spot crude traded at prices up 40 percent or more from a year ago. Will these prices hold? Five experts on oil offer their views. That's assuming the economy performs as expected - about 1 percent growth in G.N.P. The other big uncertainty is the U.S.S.R. If their production drops more than 4 percent, prices could stengthen. ", "title": "Prospects;"}
{"date": "December 31, 1989, Sunday, Late Edition - Final", "body": "DATELINE: WASHINGTON, Dec. 30 For years, experts have dubbed Czechoslovakia's spy agency the ''two Czech'' service. But he cautioned against euphoria. ''The Soviets wouldn't have relied on just official cooperation,'' he said. ''It would be surprising if they haven't unilaterally penetrated friendly services with their own agents, too.'' ", "title": "Upheaval in the East: Espionage;"}
{"date": "December 31, 1989, Sunday, Late Edition - Final", "body": "SURVIVING the decline in the economy will be the overriding issue for 1990, say leaders of the county's business community. Successful Westchester business owners will face and overcome these risks and obstacles. Westchester is a land of opportunity for the business owner. ", "title": "Coping With the Economic Prospects of 1990"}

Answer 1

Here you go:
require(jsonlite)
filelist <- c("NYT_1989.json","NYT_1990.json","NYT_1991.json",
"WP_1989.json", "WP_1990.json","WP_1991.json",
"USAT_1989.json","USAT_1990.json","USAT_1991.json")
newJSON <- sapply(filelist, function(x) fromJSON(readLines(x)))
Read in just the body entry from each line of the input file.
You asked about how to just read in a subset of the JSON file. The file data referenced isn't actually JSON format. It is JSON like, hence we have to modify the input to fromJSON() to correctly read in the data. We dereference the result from fromJSON()$body to extract just the body variable.
filelist <- c("./data/NYT_1989.json", "./data/NYT_1990.json")
newJSON <- sapply(filelist, function(x) fromJSON(sprintf("[%s]", paste(readLines(x), collapse = ",")), flatten = FALSE)$body)
newJSON
Results
> filelist <- c("./data/NYT_1989.json", "./data/NYT_1990.json")
> newJSON <- sapply(filelist, function(x) fromJSON(sprintf("[%s]", paste(readLines(x), collapse = ",")), flatten = FALSE)$body)
> newJSON
./data/NYT_1989.json
[1,] "Frigid temperatures across much of the United States this month sent demand for heating oil soaring, providing a final upward jolt to crude oil prices. Some spot crude traded at prices up 40 percent or more from a year ago. Will these prices hold? Five experts on oil offer their views. That's assuming the economy performs as expected - about 1 percent growth in G.N.P. The other big uncertainty is the U.S.S.R. If their production drops more than 4 percent, prices could stengthen. "
[2,] "DATELINE: WASHINGTON, Dec. 30 For years, experts have dubbed Czechoslovakia's spy agency the ''two Czech'' service. But he cautioned against euphoria. ''The Soviets wouldn't have relied on just official cooperation,'' he said. ''It would be surprising if they haven't unilaterally penetrated friendly services with their own agents, too.'' "
[3,] "SURVIVING the decline in the economy will be the overriding issue for 1990, say leaders of the county's business community. Successful Westchester business owners will face and overcome these risks and obstacles. Westchester is a land of opportunity for the business owner. "
./data/NYT_1990.json
[1,] "Blue temperatures across much of the United States this month sent demand for heating oil soaring, providing a final upward jolt to crude oil prices. Some spot crude traded at prices up 40 percent or more from a year ago. Will these prices hold? Five experts on oil offer their views. That's assuming the economy performs as expected - about 1 percent growth in G.N.P. The other big uncertainty is the U.S.S.R. If their production drops more than 4 percent, prices could stengthen. "
[2,] "BLUE1: WASHINGTON, Dec. 30 For years, experts have dubbed Czechoslovakia's spy agency the ''two Czech'' service. But he cautioned against euphoria. ''The Soviets wouldn't have relied on just official cooperation,'' he said. ''It would be surprising if they haven't unilaterally penetrated friendly services with their own agents, too.'' "
[3,] "GREEN4 the decline in the economy will be the overriding issue for 1990, say leaders of the county's business community. Successful Westchester business owners will face and overcome these risks and obstacles. Westchester is a land of opportunity for the business owner. "
You might find the following apply tutorial useful:
Datacamp: R tutorial on the Apply family of functions
I also recommend reading:
R Inferno - Chapter 4 - Over-Vectorizing
trust my when I say this online free book has helped me a lot. It has also confirmed I am an idiot on multiple occasions :-)