比較相同長度但不同水平的兩個因子

Question

是否可以比較R中相同長度不同水平的兩個因子？

A: Factor w/207 levels, length 2000 
B: Factor w/224 levels, length 2000 

運行此行代碼

mean(A == B) 

給了我以下錯誤：

Error in Ops.factor(A, B) : level sets of factors are different

Answer 1

轉換爲字符，然後比較：

# data 
A <- factor(1:5) 
B <- factor(c(1:3,6,6)) 

str(A) 
# Factor w/ 5 levels "1","2","3","4",..: 1 2 3 4 5 
str(B) 
# Factor w/ 4 levels "1","2","3","6": 1 2 3 4 4 

mean(A == B) 

Error in Ops.factor(A, B) : level sets of factors are different

mean(as.character(A) == as.character(B)) 
# [1] 0.6 

或者另一方法將是

mean(levels(A)[A] == levels(B)[B]) 

其上的1E8數據集更慢的2倍。