将行从一个df复制到另一个行中的每个行 [英] Copying row from one df into everyone row in another

问题描述

我有两个数据框

一个df仅是包含列的一行：

One df being just one row containing columns:

Description | Location
   Red      |  NH

第二个df包含多个包含列的行（假设是3行）：

The second df containing multiple rows (lets say 3 rows) that contain columns:

Item_Num | Quantity | Rating | 
    01   |    2     |   A    |
    02   |    5     |   B    |
    03   |    4     |   B+   |

我要创建它，以便第一个df中的第一行对

I want to make it so that the first row in the first df is repeating for every row in the second.

   Description  | Location | Item_Num | Quantity | Rating | 
       Red      |  NH      |    01    |    2     |   A    |
       Red      |  NH      |    02    |    5     |   B    |
       Red      |  NH      |    03    |    4     |   B+   |

我尝试玩循环，但遇到错误。加入他们并没有为我工作，也没有加入键

I tried playing around with loops but get an error. Joining them hasn't been working for me and there is no join key

推荐答案

一种选择是使用 tidyr 包中的> crossing 函数，该函数创建2个数据集的行的组合：

One option is to use crossing function from tidyr package, which creates combinations of rows of 2 datasets:

# example datasets
df1 = data.frame(Description = "Red",
                 Location = "NH")

df2 = data.frame(Item = 1:3,
                 Rating = c(20,25,30))

library(tidyr)

crossing(df1, df2)

#   Description Location Item Rating
# 1         Red       NH    1     20
# 2         Red       NH    2     25
# 3         Red       NH    3     30

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