merge two data frames with different number of rows and repeat same value for same column-CodePudding

I have two data frames named df1 and df2 with different number of rows. in these two data frames, I have three identical columns but with different sizes.

df1<- data_frame(id= c(1,2,2,3,3,3,5,5,4,4), num=c(10,20,20,30,30,30,50,50,40,40), age=c(31,32,32,33,33,33,35,35,34,34),
                 c=c(95,96,96,97,97,97,99,99,98,98))
                   
df2<- data_frame(id=1:5, num=c(10,20,30,40,50), age=31:35,a=11:15,b=10.5:14.5)

I want to merge df1 with df2 based on identical column in such a way that values in column a and b in df2 repeat based on corresponding columns in df1. my expected output would be like this:

     id   num   age     c     a     b
    <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
 1     1    10    31    95    11  10.5
 2     2    20    32    96    12  11.5
 3     2    20    32    96    12  11.5
 4     3    30    33    97    13  12.5
 5     3    30    33    97    13  12.5
 6     3    30    33    97    13  12.5
 7     5    50    35    99    15  14.5
 8     5    50    35    99    15  14.5
 9     4    40    34    98    14  13.5
10     4    40    34    98    14  13.5

thank you in advance

CodePudding user response：

We could use left_join this way:

library(dplyr)
left_join(df1, df2, by="id") %>% 
  select(-ends_with(".y"), num = num.x, age=age.x)

      id   num   age     c     a     b
   <dbl> <dbl> <dbl> <dbl> <int> <dbl>
 1     1    10    31    95    11  10.5
 2     2    20    32    96    12  11.5
 3     2    20    32    96    12  11.5
 4     3    30    33    97    13  12.5
 5     3    30    33    97    13  12.5
 6     3    30    33    97    13  12.5
 7     5    50    35    99    15  14.5
 8     5    50    35    99    15  14.5
 9     4    40    34    98    14  13.5
10     4    40    34    98    14  13.5