如何从R中每个日期的一列值中为每个特定值创建一个数据框？

我拥有的数据帧格式如下：

dates <- c("02/27/92", "02/27/92", "02/28/92", "02/28/92", "02/28/92", "02/29/92", "02/29/92")

df_Before <- data.frame(Date = as.Date(dates, "%m/%d/%y"),
             ID = c(1,1,2,2,2,3,3),
             Var1 = factor(c('d','c','d','b','c','a','b')))
> df_Before
  Date     ID  Var1
1 1992-02-27  1    d
2 1992-02-27  1    c
3 1992-02-28  2    d
4 1992-02-28  2    b
5 1992-02-28  2    c
6 1992-02-29  3    a
7 1992-02-29  3    b

---

提前谢谢

Reforme2库具有此类型应用程序的dcast函数

library(reshape2)
dcast(df_Before, Date+ID~Var1, length)

#        Date ID a b c d
#1 1992-02-27  1 0 0 1 1
#2 1992-02-28  2 0 1 1 1
#3 1992-02-29  3 1 1 0 0

---

您可以使用

cast

功能来执行此操作，这是一个更基本的R:

library(reshape)

df_Before$values <- 1 # Need to add this one column in order to aggregate.
df_After <- cast(df_Before, formula = Date + ID ~ Var1, sum, value = "values")

---

没关系，其他人在上面的

dcast

中发布了一个更好的

library(reshape)

df_Before$values <- 1 # Need to add this one column in order to aggregate.
df_After <- cast(df_Before, formula = Date + ID ~ Var1, sum, value = "values")

> df_After
        Date ID a b c d
1 1992-02-27  1 0 0 1 1
2 1992-02-28  2 0 1 1 1
3 1992-02-29  3 1 1 0 0