Question

我一直在尝试学习R，我有一个包含单行JSON对象的JSON文件，并且每个对象都有一组帐户数据。我想做的是解析每一行，然后从解析的JSON对象中获取JSON数组，提取帐户类型和金额。但是我的问题是我不知道如何最好地仅抽取这两个属性。

我尝试使用dplyr包从每个JSON行中提取“ accountHistory”，但出现控制台错误。当我尝试时：

select(JsonAcctData, "accountHistory.type", "accountHistory.amount")

发生的是，我的代码仅返回每行类型和金额的最后一个帐户。

现在我的代码正在写入一个csv文件，我可以看到我需要的所有数据，但是我只想删除ext

library("rjson")
library("dplyr")

parseJsonData <- function (sourceFile, outputFile) 
{
  #Get all total lines in the source file provided
  totalLines <- readLines(sourceFile)

  #Clean up old output file
  if(file.exists(outputFile)){
    file.remove(outputFile)
  }

  #Loop over each line in the sourceFile, 
  #parse the JSON and append to DataFrame
  JsonAcctData <- NULL
  for(i in 1:length(totalLines)){
    jsonValue <- fromJSON(totalLines[[i]])
    frame <- data.frame(jsonValue)
    JsonAcctData <- rbind(JsonAcctData, frame)
  }

  #Try to get filtered data
  filteredColumns <- 
    select(JsonAcctData, "accountHistory.type", "accountHistory.amount")
  print(filteredColumns)

  #Write the DataFrame to the output file in CSV format
  write.csv(JsonAcctData, file = outputFile)

}

测试JSON文件数据：

{"name":"Test1", "accountHistory":[{"amount":"107.62","date":"2012-02- 
  02T06:00:00.000Z","business":"CompanyA","name":"Home Loan Account 
  6220","type":"payment","account":"11111111"}, 
  {"amount":"650.88","date":"2012-02- 
  02T06:00:00.000Z","business":"CompanyF","name":"Checking Account 
  9001","type":"payment","account":"123123123"}, 
  {"amount":"878.63","date":"2012-02- 
  02T06:00:00.000Z","business":"CompanyG","name":"Money Market Account 
  8743","type":"deposit","account":"123123123"}]}
  {"name":"Test2", "accountHistory":[{"amount":"199.29","date":"2012-02-            
  02T06:00:00.000Z","business":"CompanyB","name":"Savings Account 
  3580","type":"invoice","account":"12312312"}, 
  {"amount":"841.48","date":"2012-02- 
  02T06:00:00.000Z","business":"Company","name":"Home Loan Account 
  5988","type":"payment","account":"123123123"}, 
  {"amount":"116.55","date":"2012-02- 
  02T06:00:00.000Z","business":"Company","name":"Auto Loan Account 
  1794","type":"withdrawal","account":"12312313"}]}

我希望得到一个csv，该csv仅包含帐户类型和每个帐户中持有的金额。

Answer 1

这是使用regex（在base R中）的一种方式

# read json 
json <- readLines('test.json', warn = FALSE)
# extract with regex
amount <- grep('\"amount\":\"\\d+\\.\\d+\"', json, value = TRUE)
amount <- as.numeric(gsub('.*amount\":\"(\\d+\\.+\\d+)\".*', '\\1', amount, perl = TRUE))
type   <- grep('\"type\":\"\\w+\"', json, value = TRUE)
type   <- gsub('.*type\":\"(\\w+)\".*', '\\1', type, perl = TRUE)
# output
data.frame(type, amount)
#         type amount
# 1    payment 107.62
# 2    payment 650.88
# 3    deposit 878.63
# 4    invoice 199.29
# 5    payment 841.48
# 6 withdrawal 116.55

如何在JSON对象中循环遍历JSON数组

1 个答案: