R在列中拆分值

Question

我有这个数据框

 d              f         
 "first tweet"  A
 "second tweet" B
 "thrid tweet"  C 

我想得到这个

 d              A      B       C         
 "first tweet"  1      0       0
 "second tweet" 0      1       0
 "thrid tweet"  0      0       1

谢谢!

Answer 1

以下是一些需要考虑的选项:

1. model.matrix

   cbind(mydf, model.matrix(~ 0 + f, data = mydf))
   #              d f fA fB fC
   # 1  first tweet A  1  0  0
   # 2 second tweet B  0  1  0
   # 3  thrid tweet C  0  0  1
   

2. table

   cbind(mydf, as.data.frame.matrix(table(sequence(nrow(mydf)), mydf$f)))
   #              d f A B C
   # 1  first tweet A 1 0 0
   # 2 second tweet B 0 1 0
   # 3  thrid tweet C 0 0 1
   

3. dcast 来自"reshape2"

   library(reshape2)
   dcast(mydf, d ~ f, value.var="f", fun.aggregate=length)
   #              d A B C
   # 1  first tweet 1 0 0
   # 2 second tweet 0 1 0
   # 3  thrid tweet 0 0 1
   

请注意,前两个选项与第三个选项之间存在差异.如果恰好有列"d"的重复值,则第三个选项将折叠(和制表)值,而前两个选项将逐行拆分值.