Hi all,

Let's say I have a data.frame and wants to turn each of it's columns into a
factor.
My instinct would be to use as.factor with apply. But this won't work, and
result with a data.frame of characters.
I found another solution for how to achieve this, but I would also like to
understand - *WHY* does it work this way?

Here is an example script:
a <- data.frame(x1 = rnorm(100), x2 = sample(c("a","b"), 100, replace = T),
x3 = factor(c(rep("a",50) , rep("b",50))))
apply(a2, 2,class) # why is column 3 not a factor ?
a[,3]  # since it IS a factor.
a2 <- apply(a, 2,as.factor) # won't work - why not ?
a2[,3]  # Why was this just turned into a character ???
# A solution
a2 <- lapply(a, as.factor)
a3 <- as.data.frame(a2)
str(a3)


Thanks,
Tal



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