将 Elastic 包（嵌套列表？）的 R 输出转换为 data.frame 或 JSON

我正在使用 R 和“elastic”包来查询包含 JSON 格式的 Twitter 数据的弹性搜索数据库。查询工作正常，我得到了我期望的输出内容（out）。

class(out) 
[1] "list"

和 out$hits$hits 返回

> out$hits$hits
[[1]]
[[1]]$`_index`
[1] "twitter_all_geo-2014-11-01"

[[1]]$`_type`
[1] "ctweet"

[[1]]$`_id`
[1] "ubicity-twitter-160f0964-6fc7-43ef-af2a-0e1b8c8184c7"

[[1]]$`_version`
[1] 1

[[1]]$`_score`
[1] 2.10757

[[1]]$`_source`
[[1]]$`_source`$id
[1] "528330489049120770"

[[1]]$`_source`$created_at
[1] "2014-10-31T23:39:39+0000"

[[1]]$`_source`$user
[[1]]$`_source`$user$name
[1] "afterlifetemis"


[[1]]$`_source`$place
[[1]]$`_source`$place$geo_point 
[[1]]$`_source`$place$geo_point[[1]]
[1] 30.4529

[[1]]$`_source`$place$geo_point[[2]]
[1] 50.61104


[[1]]$`_source`$place$city
[1] "Ukraine"

[[1]]$`_source`$place$country
[1] "Ukraine"

[[1]]$`_source`$place$country_code
[1] "UA"

[[1]]$`_source`$msg
[[1]]$`_source`$msg$text
[1] "u had one job artemis\none"

[[1]]$`_source`$msg$lang
[1] "EN"

[[1]]$`_source`$msg$hash_tags
list()

[[2]]
[[2]]$`_index`
[1] "twitter_all_geo-2014-11-01"

[[2]]$`_type`
[1] "ctweet"
...
...

基本上我想将数据保存为 .csv 文件，所以我输入

> write.csv(out$hits$hits,'out.csv')
Error in data.frame(text = "u had one job artemis\none", lang = "EN",   : arguments imply differing number of rows: 1, 0

我认为有必要将其转换为 data.frame，所以我尝试：

> df <- ldply (out, data.frame)

data.frame 中的错误（文本 =“你有一份工作 artemis\none”，lang =“EN”，： 参数意味着不同的行数：1、0

（我也尝试了其他几种乐观的尝试，比如这个：）

> t(sapply(out$hits$hits, '[', 1:max(sapply(out$hits$hits, length))))
  _index                       _type    _id                                                        _version _score  _source
[1,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-160f0964-6fc7-43ef-af2a-0e1b8c8184c7" 1        2.10757 List,5 
[2,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-ba071fff-cafb-4d3f-947d-13c934905c1b" 1        2.10757 List,5 
[3,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-dd64af32-4d59-4008-a3db-74471ad269d1" 1        2.10757 List,5 
[4,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-4ba0d3d0-642d-4f9f-aaf9-c55929c35dc4" 1        2.10757 List,5 
[5,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-d7b8cbbc-87b3-44b5-8c9c-91c7b62f1458" 1        2.10757 List,5 
[6,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-76353a7c-44c9-4863-a59d-adb16716ca18" 1        2.10757 List,5 
[7,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-2aec0798-9918-4b66-9b2a-ef5a4d1f3711" 1        2.10757 List,5 
[8,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-c9e7637d-358a-40ee-a06c-85af04c22191" 1        2.10757 List,5 
[9,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-8928c1ef-f46a-4682-99c4-4dbc55270b03" 1        2.10757 List,5 
[10,] "twitter_all_geo-2014-11-01" "ctweet" "ubicity-twitter-d6b19975-b310-46c4-af11-af56971b7c4b" 1        2.10757 List,5 

一开始看起来不错，但实际的推文消息不再在矩阵中

我很乐观，认为可能首先将其转换（返回）为 JSON（使用 RJSON）

toJSON（输出） toJSON(out) 中的错误：无法转义字符串。字符串不是utf8

最后我有一个列表，无法保存，无法转换为 JSON、data.frame 或 data.table （因为它不统一）。有谁可以给​​我一个提示：a) 将其转换为 JSON 或如何将列表保存到 .csv 文件或将其放入 data.frame 中？

非常感谢，我想我不太明白。

-Tobias

I think unlist() and matrix()可以完成这项工作。

转换的示例Search()-return out进入数据框：

# get the first 3 hits from elasticsearch store
out <- Search(index="shakespeare", size=3)

# (optional) verify that all hits expand to the same length
# (should be true for data intended to be in a table format)
stopifnot(
    sapply(
        out$hits$hits, 
        function(x) {!(length(unlist(x)) - length(unlist(out$hits$hits[[1]])))}
    )
)

# count number of columns, use unlist() to convert 
# nested lists to a vector, use the first hit as proxy
nColumns <- length(unlist(out$hits$hits[[1]]))

# fetch column names ... as above
nNames <- names(unlist(out$hits$hits[[1]]))

# unlist all hits and convert to matrix with ncol Columns, don't forget byrow=TRUE!
df <- data.frame(matrix(unlist(out$hits$hits), ncol=nColumns, byrow=TRUE))

# setting the column names
names(df) <- nNames

# do whatever you want with df
print(df)

Cheers!