R：Web 抓取 JSON，从巢中提取信息

Question

我正在尝试使用 tidyJSON 从 JSON 中提取信息，但我愿意接受任何可以达到我目的的 R 包。我查看了文档和插图，发现complex example 很有帮助。但是，我想要的信息嵌套在非键值对中，我不知道如何访问它。我有兴趣获取appid、name、developer等，但这些信息在570和730之内：

{"570":{"appid":570,"name":"Dota 2","developer":"Valve","publisher":"Valve","score_rank":71,"owners":102151578,"owners_variance":259003,"players_forever":102151578,"players_forever_variance":259003,"players_2weeks":9436299,"players_2weeks_variance":89979,"average_forever":11727,"average_2weeks":1229,"median_forever":277,"median_2weeks":662,"ccu":811259,"price":"0","tags":{"Free to Play":22678,"MOBA":7808,"Strategy":7415,"Multiplayer":6757,"Team-Based":4848,"Action":4602,"e-sports":4089,"Online Co-Op":3669,"Competitive":3553,"PvP":2655,"RTS":2267,"Difficult":2129,"RPG":2114,"Fantasy":2044,"Tower Defense":2024,"Co-op":1898,"Character Customization":1514,"Replay Value":1487,"Action RPG":1397,"Simulation":1024}},

"730":{"appid":730,"name":"Counter-Strike: Global Offensive","developer":"Valve","publisher":"Valve","score_rank":78,"owners":29225079,"owners_variance":154335,"players_forever":28552354,"players_forever_variance":152685,"players_2weeks":9102348,"players_2weeks_variance":88410,"average_forever":17648,"average_2weeks":791,"median_forever":5030,"median_2weeks":358,"ccu":543626,"price":"1499","tags":{"FPS":17082,"Multiplayer":13744,"Shooter":12833,"Action":10881,"Team-Based":10369,"Competitive":9664,"Tactical":8529,"First-Person":7329,"e-sports":6716,"PvP":6383,"Online Co-Op":5714,"Military":4621,"Co-op":4435,"Strategy":4424,"War":4361,"Realistic":3196,"Trading":3191,"Difficult":3158,"Fast-Paced":3100,"Moddable":2496}}

有成千上万个这样的条目。有没有办法跳过“顶级”并在巢中查看？
JSON信息来自http://steamspy.com/api.php?request=top100in2weeks

Answer 1

这可能是你需要的：

library(jsonlite)
data = fromJSON("http://steamspy.com/api.php?request=top100in2weeks")

appid = lapply(data, function(x){x$appid})
name = lapply(data, function(x){x$name})

df = data.frame(appid = unlist(appid),
                name = unlist(name),
                stringsAsFactors = F)

结果：

> head(df)
        appid                             name
570       570                           Dota 2
730       730 Counter-Strike: Global Offensive
578080 578080    PLAYERUNKNOWN'S BATTLEGROUNDS
440       440                  Team Fortress 2
271590 271590               Grand Theft Auto V
433850 433850           H1Z1: King of the Kill

我会让你添加其余的信息

编辑：将数组添加到数据框

可以在数据框中为每个游戏添加标签信息。以及时间标记。对于每个游戏，您必须在一列中存储一组标签名称，在另一列中存储标签数量。

在df的定义后添加以下几行：

for(k in 1:nrow(d)){
    d$tags[k] = list(names(data[[k]]$tags))
    d$tagsQ[k] = list(unlist(data[[k]]$tags))
}

这会给你：

> d["570",]
    appid   name
570   570 Dota 2

tags
570 Free to Play, MOBA, Strategy, Multiplayer, Team-Based, Action, e-sports, Online Co-Op, Competitive, PvP, RTS, Difficult, RPG, Fantasy, Tower Defense, Co-op, Character Customization, Replay Value, Action RPG, Simulation

tagsQ
570 22686, 7810, 7420, 6759, 4850, 4603, 4092, 3672, 3555, 2657, 2267, 2130, 2116, 2045, 2024, 1898, 1514, 1487, 1397, 1023

在这种情况下，tags 和 tagsQ 列包含列表。要获取appid 570 的第二个标签和数量，请执行以下操作：

> df["570","tags"][[1]][2]
[1] "MOBA"

> d["570","tagsQ"][[1]][2]
MOBA 
7810