r - 通过 R 中的 2 个变量合并数据

Question

我正在尝试合并两个数据集。过去我用过 merge()与 by等于我想合并的变量。但是，现在我想用两个变量来做到这一点。我的第一个数据集看起来像这样:

Year   Winning_Tm    Losing_Tm
2011   Texas         Washington
2012   Alabama       South Carolina
2013   Tennessee     Texas

然后我有另一个数据集，其中包含每年每个团队的排名(这是非常简化的)。像这样:

Year    Team             Rank
2011    Texas            32
2011    Washington       34
2012    South Carolina   45
2012    Alabama          12
2013    Texas            6
2013    Tennessee        51

我想合并它们，所以我有一个如下所示的数据集:

Year   Winning_Tm    Winning_TM_rank    Losing_Tm        Losing_Tm_rank
2011   Texas         32                 Washington       34
2012   Alabama       12                 South Carolina   45
2013   Tennessee     51                 Texas            6

我希望有一种简单的方法可以做到这一点，但它可能更复杂。谢谢!

Answer 1

我复制了你的数据(下次尝试包含它的 dput):

A <- data.frame(
  Year = c(2011, 2012, 2013),
  Winning_Tm = c("Texas","Alabama","Tennessee"),
  Losing_Tm = c("Washington","South Carolina", "Texas"),
  stringsAsFactors = FALSE
)

B <- data.frame(
  Year = c("2011","2011","2012","2012","2013","2013"),
  Team = c("Texas","Washington","South Carolina","Alabama","Texas","Tennessee"),
  Rank = c(32,34,45,12,6,51),
  stringsAsFactors = FALSE
)

您可以 melt使用 reshape2 的第一个数据帧包裹:

library(reshape2)

A <- melt(A, id.vars = "Year")
names(A)[3] <- "Team"

现在它看起来像这样:

> A
  Year   variable           Team
1 2011 Winning_Tm          Texas
2 2012 Winning_Tm        Alabama
3 2013 Winning_Tm      Tennessee
4 2011  Losing_Tm     Washington
5 2012  Losing_Tm South Carolina
6 2013  Losing_Tm          Texas

然后，您可以按感兴趣的两列将数据集合并在一起:

AB <- merge(A, B, by=c("Year","Team"))

看起来像这样:

> AB
  Year           Team   variable Rank
1 2011          Texas Winning_Tm   32
2 2011     Washington  Losing_Tm   34
3 2012        Alabama Winning_Tm   12
4 2012 South Carolina  Losing_Tm   45
5 2013      Tennessee Winning_Tm   51
6 2013          Texas  Losing_Tm    6

然后使用 reshape来自基础 R 的命令您可以更改 AB到宽格式:

reshape(AB, idvar = "Year", timevar = "variable", direction = "wide")

结果:

  Year Team.Winning_Tm Rank.Winning_Tm Team.Losing_Tm Rank.Losing_Tm
1 2011           Texas              32     Washington             34
3 2012         Alabama              12 South Carolina             45
5 2013       Tennessee              51          Texas              6