R - 数据框切换行和列

Question

我有如下所示的数据框:

category fan_id likes
A     10702397  1
B     10702397  4
A     35003154  1
B     35003154  1
C     35003154  2 

我想将其转换为以下数据框

fan_id   A B C
10702397 1 4 0
35003154 1 1 2

我能想到的唯一方法是遍历数据框并手动构建另一个，但似乎必须有更好的方法。

似乎我想与这里提出的问题相反 Switch column to row in a data.frame

Answer 1

底座 reshape功能方法:

dat <- data.frame(
       category=c("A","B","A","B","C"),
       fan_id=c(10702397,10702397,35003154,35003154,35003154),
       likes=c(1,4,1,1,2)
                 )
result <- reshape(dat,idvar="fan_id",timevar="category",direction="wide")
names(result)[2:4] <- gsub("^.*\\.","",names(result)[2:4])
result

    fan_id A B  C
1 10702397 1 4 NA
3 35003154 1 1  2

奖金 xtabs方法:

result2 <- as.data.frame.matrix(xtabs(likes ~ fan_id + category, data=dat))

         A B C
10702397 1 4 0
35003154 1 1 2

带有修复的确切格式:

data.frame(fan_id=rownames(result2),result2,row.names=NULL)

    fan_id A B C
1 10702397 1 4 0
2 35003154 1 1 2