如何在新数据集中将因子正确转换为数值

Question

我将数据集中的因子转换为数值，如下所示

library(dplyr) 
df = data.frame(level= c( 'low', 'medium', 'high', 'very high'))

df$level = as.numeric(revalue(df$level, c('low' = 1, 'medium' =2, 'high'= 3, 'very high'=4)))
df

没关系。 当我尝试将此规则应用于新数据集时出现问题（我对模型进行了转换并希望预测新数据）

newdude = data.frame(level = c( 'high'))
newdude$level = as.numeric(revalue(newdude$level, c('low' = 1, 'medium' =2, 'high'= 3, 'very high'=4)))
Error
The following `from` values were not present in `x`: low, medium, very high 
> newdude
  level
1     1

我得到的不是1而不是3

newdude$level = as.numeric(revalue(newdude$level, c( 'high'= 3)))

因为我无法预先知道它将获得什么价值

如何解决？

Answer 1

试试吧

newdude = data.frame(level = factor('high', levels = c('low', 'medium', 'high', 'very high')))

newdude$level
[1] high
Levels: low medium high very high
as.numeric(newdude$level)
[1] 3