Question

嘿，伙计们！我有简单的R脚本来解析JSON文件：

json <- 
   rjson::fromJSON(readLines('http://data.rada.gov.ua/ogd/zpr/skl8/bills-
   skl8.json', warn=F))
bills <-  data.frame(
  id = numeric(), 
  title = character(),
  type = character(), 
  subject = character(), 
  rubric = character(),
  executive = character(),
  sesion = character(),
  result = character() 
)
for (row in json) 
{
  bill <- data.frame(
    id = row$id, 
    title = row$title, 
    type = row$type,
    subject = row$subject, 
    rubric = row$rubric,
    executive = row$mainExecutives$executive$department,
    sesion = row$registrationSession,
    result = row$currentPhase$title
)
  bills <- rbind(bills, bill)
}

但我在data.frame中有错误（id = row $ id，title = row $ title，type = row $ type，subject = row $ subject，：参数意味着不同的行数：1,0

所以，我的JSON文件在277行中有NULL值。我可以跳过此错误或替换循环中的NULL值吗？谢谢！

Answer 1

要回答你的直接问题，我会用一个小函数来包装它，如果缺少执行部门，它会返回一个字符串。

protect_against_null <- function( x ) {
  if( is.null(x) )
    return( "" ) # Replace with whatever string you'd like.
  else 
    return( x )
}

for (row in json) {
  bill <- data.frame(
    id = row$id, 
    title = row$title, 
    type = row$type,
    subject = row$subject, 
    rubric = row$rubric,
    executive = protect_against_null(row$mainExecutives$executive$department),
    sesion = row$registrationSession,
    result = row$currentPhase$title
  )
  bills <- rbind(bills, bill)
}

长期建议：由于这个数据集是11,000个嵌套记录，我会回避循环。查看purrr包，将嵌套的json / list映射到矩形数据框。特别是purrr::map_dfr()。

Answer 2

为此，fromJSON（jsonlite包）可能很方便。

library(jsonlite)

url <- 'http://data.rada.gov.ua/ogd/zpr/skl8/bills-skl8.json'
df <- jsonlite::fromJSON(url)   

df1 <- data.frame(
  id = df$id, 
  title = df$title, 
  type = df$type,
  subject = df$subject, 
  rubric = df$rubric,
  executive = df$mainExecutives$executive$department,
  sesion = df$registrationSession,
  result = df$currentPhase$title
)

在R中的JSON中跳过NULL值

2 个答案: