R 将数据框的某列中因子变量的值替换为该列的现有值

这是我的数据集：

codes<-c("a1", "b1", "c1", "a2", "b2", "c2", "a3", "b3", "c3")
dt= data.frame(codes)

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code我们可以在%

 dt$codes[dt$codes %in% c('a1', 'a2', 'a3')] <- 'c3'

dt$codes[dt$codes== “a1” || “a2” || “a3”] <- “c3”

 dt$codes[dt$codes %in% c('a1', 'a2', 'a3')] <- 'c3'

levels(dt$codes)[levels(dt$codes) %in% c('a1', 'a2', 'a3')] <- 'c3'