使用子集()时确定哪个列名导致“选择未定义的列"错误 [英] Determine which column name is causing 'undefined columns selected' error when using subset()

问题描述

我正在尝试从一个非常大的数据帧中提取一个大数据帧的子集，使用

I'm trying to subset a large data frame from a very large data frame, using

data.new <- subset(data, select = vector)

其中 vector 是一个字符串，其中包含我试图隔离的列名.当我这样做时，我得到

where vector is a character string containing the column names I'm trying to isolate. When I do this I get

Error in `[.data.frame`(x, r, vars, drop = drop) : 
  undefined columns selected

有没有办法确定向量中的哪个特定列名是未定义的?通过反复试验，我将范围缩小到大约 400 个，但这仍然无济于事.

Is there a way to identify which specific column name in the vector is undefined? Through trial and error I've narrowed it down to about 400, but that still doesn't help.

推荐答案

找到您的向量中不是 %in% 数据的 names() 的元素框架.

Find the elements of your vector that are not %in% the names() of your data frame.

工作示例:

dd <- data.frame(a=1,b=2)
subset(dd,select=c("a"))
##   a
## 1 1

现在尝试一些不起作用的东西:

Now try something that doesn't work:

v <- c("a","d")
subset(dd,select=v)
## Error in `[.data.frame`(x, r, vars, drop = drop) : 
##    undefined columns selected

v[!v %in% names(dd)]
## [1] "d"

或

setdiff(v,names(dd))
## [1] "d"

?match 中示例代码的最后几行显示了类似的情况.

The last few lines of the example code in ?match show a similar case.

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