在 R 中的 JSON 文件的循环内循环

Question

我正在尝试将一堆 JSON 文件聚合成一个用于三个来源和三年的文件。虽然到目前为止我只能通过乏味的方式做到这一点，但我相信我可以用更聪明、更优雅的方式来做到这一点。

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)

请注意，从 1989 年到 1991 年，三个文件的年份周期相同。有什么想法吗？谢谢！

PS：每个文件内的数据示例：

{"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

给你：

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)))

---

仅从输入文件的每一行读取body 条目。

您询问了如何仅读取 JSON 文件的子集。引用的文件数据实际上不是 JSON 格式。它类似于 JSON，因此我们必须将输入修改为 fromJSON() 才能正确读取数据。我们从fromJSON()$body 中取消引用结果以仅提取body 变量。

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

结果

> 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. "

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您可能会发现以下应用教程很有用：

• Datacamp: R tutorial on the Apply family of functions

我也推荐阅读：

• R Inferno - 第 4 章 - 过度矢量化

当我说这本在线免费书籍对我帮助很大时，请相信我。它还多次证实我是个白痴:-)