是否有R函数来获取JSON文件中括号中的值？

Question

我正在尝试使用R在JSON文件中获取一些数据，但是当数据放在方括号和键下时，它不起作用，我获取了很多数据，问题实际上是在获取“已发布”参数。示例：

{
"index": [
    {
      "id": "a979eb2b85d6c13086b29a21bdc421b2673379a4",
      "date": "2019-03-22T01:20:01-0300",
      "status": "OK",
      "sensor": [
        {
          "id": "15",
          "number": 127,
          "callback": { 
            "released": true #it is not possible to return this data
          }
        }
      ]
    },
    {
      "id": "db2890f501a3a49ed74aeb065168e057c3fd51d2",
      "date": "2019-03-25T01:20:01-0300",
      "status": "NOK",
      "sensor": [
        {
          "id": "15",
          "number": 149,
          "callback": {
            "released": false #it is not possible to return this data
          }
        }
      ]
    }
    ]
  }

遵循代码：

library(jsonlite) 
data <- fromJSON("Desktop/json/file.json")

pagination <- list()
for(i in 0:10){  
  pagination[[i+1]] <- data$index$sensor$callback
}

data_org <- rbind_pages(pagination)
nrow(data_org)
length <- nrow(data_org)
data_org[1:length, c("released")]

响应是：

nrow(data_org)
# [1] 0
data_org[1:length, c("released")]
# NULL