将R列表转换为具有缺少/ NULL元素的数据帧 [英] Convert R list to dataframe with missing/NULL elements

问题描述

给出列表：

alist = list(
  list(name="Foo",age=22),
  list(name="Bar"),
  list(name="Baz",age=NULL)
 )

将名称和年龄列转换为数据框的最佳方式是什么，缺少值（我将按照优先顺序接受NA或）？

what's the best way to convert this into a dataframe with name and age columns, with missing values (I'll accept NA or "" in that order of preference)?

使用 ldply 的简单方法失败，因为它尝试将每个列表元素转换为数据框，但是NULL barfs因为长度不匹配。最好我现在是：

Simple methods using ldply fail because it tries to convert each list element into a data frame, but the one with the NULL barfs because the lengths don't match. Best I have at the moment is:

> ldply(alist,function(s){t(data.frame(unlist(s)))})
  name  age
1  Foo   22
2  Bar <NA>
3  Baz <NA>

但这很漂亮，数值变量成为一个因素...

but that's pretty icky and the numeric variable becomes a factor...

推荐答案

提到的注释只需要一个循环，这可以通过只是将两个循环的正文放在一起：

A comment mentioned wanting only a single loop, which can be achieved with @flodel's answer just by putting the body of the two loops together:

rbind.fill(lapply(alist, function(f) {
  as.data.frame(Filter(Negate(is.null), f))
}))

给

  name age
1  Foo  22
2  Bar  NA
3  Baz  NA

这篇关于将R列表转换为具有缺少/ NULL元素的数据帧的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！