重组数据框

Question

我使用R代表我的问题：

假设我跟随数据帧：

dates <- c("2010-01-01","2010-02-01","2010-03-01","2010-04-01",
           "2010-02-01","2010-03-01","2010-04-01","2010-05-01",
           "2010-03-01","2010-04-01","2010-05-01","2010-06-01")

data.frame(A=c(1,1,1,1,2,2,2,2,3,3,3,3),B=dates,C=c(21:32))

R为这个例子提供了数据：

   A          B  C
1  1 2010-01-01 21
2  1 2010-02-01 22
3  1 2010-03-01 23
4  1 2010-04-01 24
5  2 2010-02-01 25
6  2 2010-03-01 26
7  2 2010-04-01 27
8  2 2010-05-01 28
9  3 2010-03-01 29
10 3 2010-04-01 30
11 3 2010-05-01 31
12 3 2010-06-01 32

我需要在以下结构中转换此日期框架：

    "2010-01-01"  "2010-02-01"  "2010-03-01"  "2010-04-01"  "2010-05-01"  "2010-06-01"   
1    21            22            23            24            na            na          
2    na            25            26            27            28            na
3    na            na            29            30            30            31

有什么建议吗？ （我是新用的R并试图解决它几个小时;））

Answer 1

您可以使用reshape2包和dcast功能：

library(reshape2)
dcast(dat, A ~ B, value.var='C')

#   A 2010-01-01 2010-02-01 2010-03-01 2010-04-01 2010-05-01 2010-06-01
# 1 1         21         22         23         24         NA         NA
# 2 2         NA         25         26         27         28         NA
# 3 3         NA         NA         29         30         31         32

您也可以使用基本R函数reshape执行此操作，但我发现其语法最多会让人感到困惑！