R使用ifelse来改变因子值

问题描述

我有一个因子变量列。我需要更改因子是某个很少出现的级别的所有单元格的值。我正在使用以下代码，但它似乎不起作用：

I have a column that's a factor variable. I need to change the value of all cells where the factor is a certain rarely occurring level. I'm using the following code but it doesn't seem to be working:

test2$timeFactor <- ifelse(test2$timeFactor == '94', '-1000', test2$timeFactor)

我也是试过：

test2$timeFactor <- factor(ifelse(test2$timeFactor == '94', '-1000', test2$timeFactor))

但似乎都不起作用。我在这里找不到任何明显的东西？

but neither seems to work. Anything obvious I'm missing here?

推荐答案

你最好更改级别：

set.seed(1)
x <- factor(sample(letters[1:3],10,replace=T))
x
 [1] a b b c a c c b b a
Levels: a b c

levels(x)[which(levels(x)=="c")] <- "z"
x
 [1] a b b z a z z b b a
Levels: a b z

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