创建数据透视表

问题描述

假设我有一个数据集，如下所示，其中年份在各行中列出:

Suppose I have a dataset that looks like the following, in which years are listed down rows:

id<-c(1,1,1,2,2,2,3,3,3)
year<-c(1990, 1991, 1992, 1992, 1993, 1994, 1993, 1994, 1995)
N<-c(7,8,9,7,1,2,5,4,3)
dataset<-data.frame(cbind(id, year, N))

我希望输出如下所示，以年份作为列标题:

I'd like to have the output look like the following, with years as column headings:

id   1990   1991   1992   1993   1994   1995
1    7      8      9      0      0      0
2    0      0      7      1      2      0
3    0      0      0      5      4      3

我知道这是一个相当简单的问题，但是我一直在搞乱xtabs()，melt()和cast()，但我不太清楚.

I know this is a fairly easy problem, but I've been messing around with xtabs() and with melt() and cast(), but I can't quite get it right.

推荐答案

另一种方法:

> library(reshape2)
> dcast(dataset, id ~ year, fill=0)
# Using N as value column: use value.var to override.
  id 1990 1991 1992 1993 1994 1995
1  1    7    8    9    0    0    0
2  2    0    0    7    1    2    0
3  3    0    0    0    5    4    3

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