Question

我有一组学生c("John","Jeff","Jim","Jack","Joe","Jones")，他们每个人都参加了3个不同的班级c("Math","Science","History")，并取得了自然分数，分数在0到100之间。

因此，表应该像

Name Class   Score
Jim  Math     25
Jim  History  60
Jim  Science  80
Jeff Math     85
Jeff History  40
Jeff Science  100
...
...
...

我尝试过的是：

dt<-data.frame(
  Names=rep(c("John","Jeff","Jim","Jack","Joe","Jones"),3 ),
  Class=rep(c("Math","Science","History"),6  ),
  Grades=sample(1:100,18  ))

dt[sort(dt$Names),]

我的代码给了我

   Names   Class Grades
4   Jack    Math     73
10  Jack    Math     87
16  Jack    Math     81
2   Jeff Science     24
8   Jeff Science     79

因此，我有Math，History和Science，而不是Math，Math和Math。

但是，它不能满足我的需求。我该如何解决？

Answer 1

尝试在each中使用rep ...最佳做法是将each中的times / length-out / rep显式设置为避免意外的行为。

data.frame(
  Names=rep( c("John","Jeff","Jim","Jack","Joe","Jones"), each = 3 ),
  Class=rep(c("Math","Science","History"), times = 6  ),
  Grades=sample( 1:100,18  ) )

# Names   Class Grades
# 1   John    Math     57
# 2   John Science     23
# 3   John History     82
# 4   Jeff    Math      3
# 5   Jeff Science     65
# 6   Jeff History     37
# 7    Jim    Math     95
# 8    Jim Science     39
# 9    Jim History     16
# 10  Jack    Math     18
# 11  Jack Science     63
# 12  Jack History     53
# 13   Joe    Math     90
# 14   Joe Science     11
# 15   Joe History     77
# 16 Jones    Math     29
# 17 Jones Science     15
# 18 Jones History     19

如何在特定结构中创建数据集？

1 个答案: