Why does as.factor return a character when used inside apply?

I want to convert variables into factors using apply(): a <- data.frame(x1 = rnorm(100), x2 = sample(c(\"a\",\"b\"), 100, replace = T),

解析《胜算》中的“穆丹乌拉计划”？

谍战剧《胜算》正在热播，剧中的“牡丹乌拉计划”贯穿始终。那么，什么才是真正的“穆旦乌拉计划”？

c++ strtok problem

i\'m trying to create a map of word==>drow, like polindrom... the problem is at the final level at \"strtok\"...

刘若英的歌曲那如何是什么歌？