如何在新數據集中將因子正確轉換為數值

Question

我將數據集中的因子轉換為數值，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

沒關系。 當我嘗試將此規則應用於新數據集時出現問題（我對模型進行了轉換並希望預測新數據）

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)))

因為我無法預先知道它將獲得什么價值

如何解決？

Answer 1

試試吧

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