将字符串作为数据框列名称传递

I have a data frame called data.df with various columns say col1,col2,col3....col15. The data frame does not have a specific class attribute but any attribute could be potentially used as a class variable. I would like to use an R variable called target which points to the column number to be treated as class as follows :

我有一个名为data.df的数据框，其中包含各种列，例如col1，col2，col3 .... col15。数据框没有特定的类属性，但任何属性都可能用作类变量。我想使用一个名为target的R变量，它指向要被视为类的列号，如下所示：

target<-data.df$col3

and then use that field (target) as input to several learners such as PART and J48 (from package RWeka) :

然后使用该字段（目标）作为几个学习者的输入，例如PART和J48（来自包RWeka）：

part<-PART(target~.,data=data.df,control=Weka_control(M=200,R=FALSE))
j48<-J48(target~.,data=data.df,control=Weka_control(M=200,R=FALSE))

The idea is to be able to change 'target' only once at the beginning of my R code. How can this be done?

我的想法是能够在我的R代码开头只改变一次'目标'。如何才能做到这一点？

2 个解决方案

#1

I sometimes manage to get a lot done by using strings to reference columns. It works like this:

我有时通过使用字符串来引用列来完成很多工作。它的工作原理如下：

> df <- data.frame(numbers=seq(5))
> df
  numbers
1       1
2       2
3       3
4       4
5       5
> df$numbers
[1] 1 2 3 4 5
> df[['numbers']]
[1] 1 2 3 4 5

You can then have a variable target be the name of your desired column as a string. I don't know about RWeka, but many libraries such as ggplot can take string references for columns (e.g. the aes_string parameter instead of aes).

然后，您可以将变量目标作为所需列的名称作为字符串。我不知道RWeka，但许多库如ggplot可以为列提取字符串引用（例如aes_string参数而不是aes）。

#2

If you ask about using references in R, it is impossible.

如果你询问在R中使用引用，那是不可能的。

However, if you ask about getting a column by name not explicitly given, this is possible with [ operator, like this:

但是，如果您询问是否按名称获取未明确给出的列，则可以使用[运算符，如下所示：

theNameOfColumnIwantToGetSummaryOf<-"col3"
summary(data.df[,theNameOfColumnIwantToGetSummaryOf])

...or like that:

......或者那样：

myIndexOfTheColumnIwantToGetSummaryOf<-3
summary(data.df[,sprintf("col%d",myIndexOfTheColumnIwantToGetSummaryOf)])

#1