将不均匀的分层列表转换为数据帧 [英] converting uneven hierarchical list to a data frame

问题描述

我不认为已经被问到了，但是有没有办法将列表的信息与多层次和不均匀的结构组合成长格式的数据框架？

I don't think this has been asked yet, but is there a way to combine information of a list with multiple levels and uneven structure into a data frame of "long" format?

具体来说：

library(XML)
library(plyr)
xml.inning <- "http://gd2.mlb.com/components/game/mlb/year_2009/month_05/day_02/gid_2009_05_02_chamlb_texmlb_1/inning/inning_5.xml"
xml.parse <- xmlInternalTreeParse(xml.inning)
xml.list <- xmlToList(xml.parse)
## $top$atbat
## $top$atbat$pitch
##             des              id            type               x               y 
##          "Ball"           "310"             "B"         "70.39"        "125.20" 

其中以下是结构：

> llply(xml.list, function(x) llply(x, function(x) table(names(x))))
$top
$top$atbat
.attrs  pitch 
     1      4 
$top$atbat
.attrs  pitch 
     1      4 
$top$atbat
.attrs  pitch 
     1      5 
$bottom
$bottom$action
     b    des  event      o  pitch player      s 
     1      1      1      1      1      1      1 
$bottom$atbat
.attrs  pitch 
     1      5 
$bottom$atbat
.attrs  pitch 
     1      5 
$bottom$atbat
.attrs  pitch runner 
     1      5      1 
$bottom$atbat
.attrs  pitch runner 
     1      7      1 
$.attrs
$.attrs$num
character(0)
$.attrs$away_team
character(0)
$.attrs$

喜欢拥有来自音高类别的命名矢量的数据帧，以及正确的（顶部， atbat ，底部）。因此，由于列数不同，我需要忽略不适合数据框架的级别。这样的东西：

What I'd like to have is a data frame from the named vector from the pitch category, along with the proper (top, atbat, bottom). Therefore, I would need to ignore levels that won't fit into a data.frame due to different number of columns. Something like this:

   first second third    des     x
1    top  atbat pitch   Ball 70.29
2    top  atbat pitch Strike 69.24
3 bottom  atbat pitch    Out 67.22

有一种优雅的方式来做这个？谢谢！

Is there an elegant way of doing this? Thanks!

推荐答案

我不知道优雅，但这样做有效。更熟悉plyr的人可能会提供一个更一般的解决方案。

I don't know about elegant, but this works. Those more familiar with plyr could probably provide a more general solution.

cleanFun <- function(x) {
   a <- x[["atbat"]]
   b <- do.call(rbind,a[names(a)=="pitch"])
   c <- as.data.frame(b)
}
ldply(xml.list[c("top","bottom")], cleanFun)[,1:5]
     .id             des  id type      x
1    top            Ball 310    B  70.39
2    top   Called Strike 311    S 118.45
3    top   Called Strike 312    S  86.70
4    top In play, out(s) 313    X  79.83
5 bottom            Ball 335    B  15.45
6 bottom   Called Strike 336    S  77.25
7 bottom Swinging Strike 337    S  99.57
8 bottom            Ball 338    B 106.44
9 bottom In play, out(s) 339    X 134.76

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