如何用R中的因子分类的数据帧值创建向量？

Question

I have a data frame with values classified by levels (factors), so I want to create a vector with the values of an specific level, eg

A <- c("Case1", "Case3", "Case2", "Case3", "Case2",
       "Case1", "Case3", "Case2", "Case2", "Case3",
       "Case1", "Case1", "Case3", "Case1", "Case2")
Factors <- factor(A)
Values <- 1:15

DF <- data.frame(Factors, Values)

Values_of_Case1 <- DF$Values... ????

How to create a vector in order to obtain something like:

print(Values_of_Case1)
[1]  1  6 11 12 14

Answer 1

DF$Values[DF$Factors == "Case1"]
[1]  1  6 11 12 14

or

subset(DF, Factors=='Case1')$Values
[1]  1  6 11 12 14

should work.

If you wanted only the row index for the matches you could do:

which(DF$Factors == "Case1")
[1]  1  6 11 12 14

Which in this case is the same, but it might not be in your use case.