如何在R中将两个帧合并为一个帧

Question

我有两个data.frame，第一个是日期框架，第二个是城市框架，我正在尝试将这两个框架合并为一个。

日期范围：

date
2018/7/7
2018/7/8
2018/7/9

城市框架：

area
beijing
shanghai
guangzhou

我想要的结果是：

date             area
2018/7/7      beijing
2018/7/7      shanghai 
2018/7/7      guangzhou 
2018/7/8      beijing
2018/7/8      shanghai 
2018/7/8      guangzhou 
2018/7/9      beijing
2018/7/9      shanghai 
2018/7/9      guangzhou 

提前感谢！

Answer 1

我们可以在base R中使用expand.grid

expand.grid(df1$date, df2$area)

或来自tidyr的crossing

tidyr::crossing(df1, df2)

#   date     area     
#  <fct>    <fct>    
#1 2018/7/7 beijing  
#2 2018/7/7 guangzhou
#3 2018/7/7 shanghai 
#4 2018/7/8 beijing  
#5 2018/7/8 guangzhou
#6 2018/7/8 shanghai 
#7 2018/7/9 beijing  
#8 2018/7/9 guangzhou
#9 2018/7/9 shanghai 

data

df1 <- structure(list(date = structure(1:3, .Label = c("2018/7/7", "2018/7/8", 
"2018/7/9"), class = "factor")), class = "data.frame", row.names = c(NA, -3L))

df2 <- structure(list(area = structure(c(1L, 3L, 2L), .Label = c("beijing", 
"guangzhou", "shanghai"), class = "factor")), class = "data.frame", 
row.names = c(NA, -3L))

Answer 2

这也可以给你想要的输出：

data.frame(date = sort(rep(df1$date, length(df2$area))), area= df2$area)
#       date      area
# 1 2018/7/7   beijing
# 2 2018/7/7  shanghai
# 3 2018/7/7 guangzhou
# 4 2018/7/8   beijing
# 5 2018/7/8  shanghai
# 6 2018/7/8 guangzhou
# 7 2018/7/9   beijing
# 8 2018/7/9  shanghai
# 9 2018/7/9 guangzhou

Answer 3

在base R中，您可以使用lapply和rbind来创建它

Reduce(rbind,lapply(df1$date, function(v) data.frame(date = v, area = df2["area"])))

其中输出如下：

      date      area
1 2018/7/7   beijing
2 2018/7/7  shanghai
3 2018/7/7 guangzhou
4 2018/7/8   beijing
5 2018/7/8  shanghai
6 2018/7/8 guangzhou
7 2018/7/9   beijing
8 2018/7/9  shanghai
9 2018/7/9 guangzhou