r - 将复杂的json转换为数据集

Question

我在将复杂的 JSON 转换为数据集时遇到问题，例如:

[{
    "dateTime": 1556368322971,
    "eventName": "sampleEvent",
    "vars": [{
        "distance": 350,
        "fuel" : 300,
        "vehicleType": null
    }]
}, {
    "dateTime": 1556368322971,
    "eventName": "sampleEvent",
    "vars": [{
        "distance": 360,
        "fuel" : 290,
        "vehicleType": "bus"
    }]
}]

我已经在尝试用方法做到这一点:

result <- fromJSON(file = "./all.json")


json_file <- lapply(result, function(x) {
  x[sapply(x, is.null)] <- NA
  unlist(x)
})

但问题是所有 NULL 值都丢失了。这是非常有问题的，因为当我将它转换为 dataSet(matrix) 时，所有值都完全困惑并且没有不正确的空值。

我希望有一个数据集应该如下所示:

dateTime      | eventName   | distance | fuel | vehicleType
1556368322971 | sampleEvent | 350      | 300  | NA
1556368322971 | sampleEvent | 360      | 290  | bus

Answer 1

我们可以使用tidyr::unnest

library(tidyr)
result %>% unnest()
#      dateTime   eventName distance fuel vehicleType
#1 1.556368e+12 sampleEvent      350  300        <NA>
#2 1.556368e+12 sampleEvent      360  290         bus

---

示例数据

library(jsonlite)
result <- fromJSON("all.json")

文件 all.json 包含

[{
    "dateTime": 1556368322971,
    "eventName": "sampleEvent",
    "vars": [{
        "distance": 350,
        "fuel" : 300,
        "vehicleType": null
    }]
}, {
    "dateTime": 1556368322971,
    "eventName": "sampleEvent",
    "vars": [{
        "distance": 360,
        "fuel" : 290,
        "vehicleType": "bus"
    }]
}]