将导入的 json 数据导入数据框 [英] Getting imported json data into a data frame

问题描述

我有一个包含超过 1500 个 json 对象的文件，我想在 R 中使用这些对象.我已经能够将数据作为列表导入，但无法将其强制转换为有用的结构.我想创建一个数据框，其中包含每个 json 对象的一行和每个键值对的列.

I have a file containing over 1500 json objects that I want to work with in R. I've been able to import the data as a list, but am having trouble coercing it into a useful structure. I want to create a data frame containing a row for each json object and a column for each key:value pair.

我用这个小而假的数据集重现了我的情况:

I've recreated my situation with this small, fake data set:

[{"name":"Doe, John","group":"Red","age (y)":24,"height (cm)":182,"wieght (kg)":74.8,"score":null},
{"name":"Doe, Jane","group":"Green","age (y)":30,"height (cm)":170,"wieght (kg)":70.1,"score":500},
{"name":"Smith, Joan","group":"Yellow","age (y)":41,"height (cm)":169,"wieght (kg)":60,"score":null},
{"name":"Brown, Sam","group":"Green","age (y)":22,"height (cm)":183,"wieght (kg)":75,"score":865},
{"name":"Jones, Larry","group":"Green","age (y)":31,"height (cm)":178,"wieght (kg)":83.9,"score":221},
{"name":"Murray, Seth","group":"Red","age (y)":35,"height (cm)":172,"wieght (kg)":76.2,"score":413},
{"name":"Doe, Jane","group":"Yellow","age (y)":22,"height (cm)":164,"wieght (kg)":68,"score":902}]

数据的一些特征:

• 这些对象都包含相同数量的键值对，尽管一些值为空
• 每个对象(名称和组)有两个非数字列
• name 是唯一标识符，大约有 10 个组
• 许多名称和组词都包含空格、逗号和其他标点符号.

基于这个问题:R list(structure(list())) to data frame，我尝试了以下操作:

Based on this question: R list(structure(list())) to data frame, I tried the following:

json_file <- "test.json"
json_data <- fromJSON(json_file)
asFrame <- do.call("rbind.fill", lapply(json_data, as.data.frame))

对于我的真实数据和这个假数据，最后一行给了我这个错误:

With both my real data and this fake data, the last line give me this error:

Error in data.frame(name = "Doe, John", group = "Red", `age (y)` = 24,  : 
  arguments imply differing number of rows: 1, 0

推荐答案

你只需要用 NA 替换 NULL:

You just need to replace your NULLs with NAs:

require(RJSONIO)    

json_file <-  '[{"name":"Doe, John","group":"Red","age (y)":24,"height (cm)":182,"wieght (kg)":74.8,"score":null},
    {"name":"Doe, Jane","group":"Green","age (y)":30,"height (cm)":170,"wieght (kg)":70.1,"score":500},
    {"name":"Smith, Joan","group":"Yellow","age (y)":41,"height (cm)":169,"wieght (kg)":60,"score":null},
    {"name":"Brown, Sam","group":"Green","age (y)":22,"height (cm)":183,"wieght (kg)":75,"score":865},
    {"name":"Jones, Larry","group":"Green","age (y)":31,"height (cm)":178,"wieght (kg)":83.9,"score":221},
    {"name":"Murray, Seth","group":"Red","age (y)":35,"height (cm)":172,"wieght (kg)":76.2,"score":413},
    {"name":"Doe, Jane","group":"Yellow","age (y)":22,"height (cm)":164,"wieght (kg)":68,"score":902}]'


json_file <- fromJSON(json_file)

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

一旦每个元素都有一个非空值，就可以调用 rbind 而不会出错:

Once you have a non-null value for each element, you can call rbind without getting an error:

do.call("rbind", json_file)
     name           group    age (y) height (cm) wieght (kg) score
[1,] "Doe, John"    "Red"    "24"    "182"       "74.8"      NA   
[2,] "Doe, Jane"    "Green"  "30"    "170"       "70.1"      "500"
[3,] "Smith, Joan"  "Yellow" "41"    "169"       "60"        NA   
[4,] "Brown, Sam"   "Green"  "22"    "183"       "75"        "865"
[5,] "Jones, Larry" "Green"  "31"    "178"       "83.9"      "221"
[6,] "Murray, Seth" "Red"    "35"    "172"       "76.2"      "413"
[7,] "Doe, Jane"    "Yellow" "22"    "164"       "68"        "902"

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