从数据框中匹配和添加列

Question

问题

我如何添加由两个因素选择值的列，其中一个是另一个数据框中的行名称？

示例数据

我有以下数据框：

Country, Year, Q1          
Portugal, 2004, Yes
Portugal, 2005, Yes 
Portugal, 2008, No  
UK, 2006, Yes 
UK, 2008, No 
France, 2004, No

我想从其他数据框中添加一列；

Country, 2004,2005,2006,...
Portugal,0.15,0.25,0.14,0.21,...
Spain,0.16,0.26,0.14,0.16,...
UK,0.17,0.23,0.18,0.17,...
France,0.15,0.26,0.11,0.20,...

期望的结果

并获得如下所示的数据框；

Country, Year, Q1 , Q2         
Portugal, 2004, Yes, 0.15
Portugal, 2005, Yes, 0.25
Portugal, 2006, No , 0.14
UK, 2005, Yes , 0.23
UK, 2006, No , 0.18
France, 2004, No, 0.15

非常感谢！

Answer 1

您可以使用 merge() 函数

merge(x, y, by = intersect(names(x), names(y))

例如：

l <- c(1,2,3); d <- c("a","b","c");  a <- data.frame(col1=l, col2=d)
l <- c(1,2,3); d <- c("a2","b2","c2");  b <- data.frame(col1=l, col2=d)

然后合并（a，b，by="col1"）

您将获得：

col1 col2.x col2.y
1    1      a     a2
2    2      b     b2
3    3      c     c2

Answer 2

使用 tidyr 和 dplyr 库：

library(tidyr)
library(dplyr)

# convert df2 to df2_long format
df2_long <- 
  df2 %>%
  gather( Year, Value, -Country, convert = TRUE  )

# join df1 with df2
df1 %>%
  left_join( df2_long, by = c("Country", "Year"))

结果：

   Country Year  Q1 Value
1 Portugal 2004 Yes  0.15
2 Portugal 2005 Yes  0.25
3 Portugal 2008  No    NA
4       UK 2006 Yes  0.18
5       UK 2008  No    NA
6   France 2004  No  0.15

我使用的输入数据：

df1 <- 
  structure(list(Country = c("Portugal", "Portugal", "Portugal", 
  "UK", "UK", "France"), Year = c(2004L, 2005L, 2008L, 2006L, 2008L, 
  2004L), Q1 = c("Yes", "Yes", "No", "Yes", "No", "No")), 
  .Names = c("Country", 
  "Year", "Q1"), class = "data.frame", row.names = c(NA, -6L))

df2 <-
  structure(list(Country = c("Portugal", "Spain", "UK", "France"
  ), `2004` = c(0.15, 0.16, 0.17, 0.15), `2005` = c(0.25, 0.26, 
  0.23, 0.26), `2006` = c(0.14, 0.14, 0.18, 0.11)), .Names = c("Country", 
  "2004", "2005", "2006"), class = "data.frame", row.names = c(NA, 
-4L))

从数据框中匹配和添加列

Matching and adding column from data frame

merge

r

match