R中的合并因子级别数据表方式

Question

我的一个名为type的变量看起来像这样：

$ type              : Factor w/ 4 levels "","a","e","u": 

我想将变量type的空因子水平与因子水平"u"合并

我已经使用函数levels来实现这一目标，但是我对此解决方案并不感到满意。

levels(mydata$type) = list( u = "", a = "a", e = "e", u = "u")

是否有更多类似于“ data.table”的解决方案来合并R中因子变量的级别？

Answer 1

您的方法：

library(data.table)
set.seed(100)
mydata = data.table(x = runif(20),
type=factor(sample(c("","a","e","u"),20,replace=TRUE)))
levels(mydata$type) = list( u = "", a = "a", e = "e", u = "u")
table(mydata$type)

 u  a  e 
11  4  5 

str(mydata$type)
 Factor w/ 3 levels "u","a","e": 3 1 2 1 1 3 3 1 2 1 ...

我不知道使用replace是否像data.table一样，但是您本质上需要转换回字符，进行替换和重构：

set.seed(100)
mydata = data.table(x = runif(20),
type=factor(sample(c("","a","e","u"),20,replace=TRUE)))
mydata[,type :=droplevels(replace(type,type=="","u"))]

table(mydata$type)
 a  e  u 
 4  5 11

str(mydata$type)
 Factor w/ 3 levels "a","e","u": 2 3 1 3 3 2 2 3 1 3 ...