r-如何压平从jsonlite返回的嵌套数据帧

Question

我正在用jsonlite 加载此JSON数据

<snip>  
"rawData": {
    "fortune": {}, 
    "plaintext": {}, 
    "db": {}, 
    "update": {
      "duda": [
        {
          "latencyAvg": "201.40us", 
          "latencyMax": "727.00us", 
          "latencyStdev": "54.85us", 
          "totalRequests": 561810, 
          "startTime": 1413890149, 
          "endTime": 1413890164
        }
      ]
      }, 
    "json": {
      "duda": [
        {
          "latencyAvg": "201.40us", 
          "latencyMax": "727.00us", 
          "latencyStdev": "54.85us", 
          "totalRequests": 561810, 
          "startTime": 1413890149, 
          "endTime": 1413890164
        }
      ]
    }, 
    "query": {}
  }

这导致了具有嵌套数据帧的结构

data <- structure(list(fortune = structure(list(), .Names = character(0)), 
    plaintext = structure(list(), .Names = character(0)), db = structure(list(), .Names = character(0)), 
    update = structure(list(duda = structure(list(latencyAvg = "201.40us", 
        latencyMax = "727.00us", latencyStdev = "54.85us", totalRequests = 561810L, 
        startTime = 1413890149L, endTime = 1413890164L), .Names = c("latencyAvg", 
    "latencyMax", "latencyStdev", "totalRequests", "startTime", 
    "endTime"), class = "data.frame", row.names = 1L)), .Names = "duda"), 
    json = structure(list(duda = structure(list(latencyAvg = "201.40us", 
        latencyMax = "727.00us", latencyStdev = "54.85us", totalRequests = 561810L, 
        startTime = 1413890149L, endTime = 1413890164L), .Names = c("latencyAvg", 
    "latencyMax", "latencyStdev", "totalRequests", "startTime", 
    "endTime"), class = "data.frame", row.names = 1L)), .Names = "duda"), 
    query = structure(list(), .Names = character(0))), .Names = c("fortune", 
"plaintext", "db", "update", "json", "query"))

我想创建一个看起来像这样的单一数据帧：

Type   | Name | latencyAvg | latencyMax | latencyStdev | totalRequests | startTime | endTime
json   | duda | 201.40us   | <etc..>
update | duda | 201.40us   | <etc..>

通过扁平化嵌套的数据帧。我正在想办法手动做到这一点，删除我想要的项目，并使用rbind/cbind将它们移动到一个新的数据帧中，但有没有一种简单的方法可以实现这种类型的递归扁平化？

Answer 1

使用flatten函数。它获取一个数据帧并返回一个平面数据帧。如果需要从源数据帧中排除某些列，则使用df[[-i]]排除列i。

Answer 2

假设对象被命名为"data"的不幸名称：

newdat <- rbind.data.frame( Type= c(rep("json",   nrow(data$json$duda)), 
                                    rep("update", nrow(data$update$duda)) ), 
                            rbind( data$json$duda, data$update$duda) )

Answer 3

另一个oneliner

do.call(rbind, lapply(data[c('json', 'update')], '[[', 'duda'))