如何将变量重新编码为数字？

Question

> library(car)

> df = data.frame(value=c('A', 'B', 'C', 'A'))
> foo = recode(df$value, "'A'=1; 'B'=2; 'C'=3;", as.numeric.result=TRUE)
> mean(foo)
[1] NA
Warning message:
In mean.default(foo) : argument is not numeric or logical: returning NA
> foo
[1] 1 2 3 1
Levels: 1 2 3

啊.我认为as.numeric.result(默认为TRUE)的定义是,如果结果都是数字,它们将被强制转换为数字.

如何将此重新编码的结果设为数字？

Answer 1

如果仔细查看文档,recode您会看到:

as.factor.result     return a factor; default is TRUE if var is a factor, FALSE otherwise.
as.numeric.result    if TRUE (the default), and as.factor.result is FALSE, 
                      then the result will be coerced to numeric if all values in the 
                      result are numerals—i.e., represent numbers.

所以你需要指定as.factor.result=FALSE我认为:

foo = recode(df$value, "'A'=1; 'B'=2; 'C'=3;", as.factor.result=FALSE)

编辑 由于默认as.numeric.result值为TRUE,您只需指定as.factor.result=FALSE,而不是同时指定它们.