r - R如何将级别之一更改为NA

Question

我有一个数据集，其列之一具有因子水平"a" "b" "c" "NotPerformed"。如何将所有"NotPerformed"因素更改为NA？

Answer 1

将级别设置为NA：

x <- factor(c("a", "b", "c", "NotPerformed"))
x
## [1] a            b            c            NotPerformed
## Levels: a b c NotPerformed
levels(x)[levels(x)=='NotPerformed'] <- NA
x
## [1] a    b    c    <NA>
## Levels: a b c

请注意，因子级别已删除。