Dplyr, join successive dataframes to pre-existing columns, summing their values - r

Question

I want to perform multiple joins to original dataframe, from the same source with different IDs each time. Specifically I actually only need to do two joins, but when I perform the second join, the columns being joined already exist in the input df, and rather than add these columns with new names using the .x/.y suffixes, I want to sum the values to the existing columns. See the code below for the desired output.
# Input data:
values <- tibble(
id = LETTERS[1:10],
variable1 = 1:10,
variable2 = (1:10)*10
)
df <- tibble(
twin_id = c("A/F", "B/G", "C/H", "D/I", "E/J")
)
> values
# A tibble: 10 x 3
id variable1 variable2
<chr> <int> <dbl>
1 A 1 10
2 B 2 20
3 C 3 30
4 D 4 40
5 E 5 50
6 F 6 60
7 G 7 70
8 H 8 80
9 I 9 90
10 J 10 100
> df
# A tibble: 5 x 1
twin_id
<chr>
1 A/F
2 B/G
3 C/H
4 D/I
5 E/J
So this is the two joins:
joined_df <- df %>%
tidyr::separate(col = twin_id, into = c("left_id", "right_id"), sep = "/", remove = FALSE) %>%
left_join(values, by = c("left_id" = "id")) %>%
left_join(values, by = c("right_id" = "id"))
> joined_df
# A tibble: 5 x 7
twin_id left_id right_id variable1.x variable2.x variable1.y variable2.y
<chr> <chr> <chr> <int> <dbl> <int> <dbl>
1 A/F A F 1 10 6 60
2 B/G B G 2 20 7 70
3 C/H C H 3 30 8 80
4 D/I D I 4 40 9 90
5 E/J E J 5 50 10 100
And this is the output I want, using the only way I can see to get it:
output_df_wanted <- joined_df %>%
mutate(
variable1 = variable1.x + variable1.y,
variable2 = variable2.x + variable2.y) %>%
select(twin_id, left_id, right_id, variable1, variable2)
> output_df_wanted
# A tibble: 5 x 5
twin_id left_id right_id variable1 variable2
<chr> <chr> <chr> <int> <dbl>
1 A/F A F 7 70
2 B/G B G 9 90
3 C/H C H 11 110
4 D/I D I 13 130
5 E/J E J 15 150
I can see how to get what I want using a mutate statement, but I will have a much larger number of variables in the actually dataset. I am wondering if this is the best way to do this.

Answer 1

You can try reshaping your data and using dplyr::summarise_at:
library(tidyr)
library(dplyr)
df %>%
separate(col = twin_id, into = c("left_id", "right_id"), sep = "/", remove = FALSE) %>%
pivot_longer(-twin_id) %>%
left_join(values, by = c("value" = "id")) %>%
group_by(twin_id) %>%
summarise_at(vars(starts_with("variable")), sum) %>%
separate(col = twin_id, into = c("left_id", "right_id"), sep = "/", remove = FALSE)
## A tibble: 5 x 5
# twin_id left_id right_id variable1 variable2
# <chr> <chr> <chr> <int> <dbl>
#1 A/F A F 7 70
#2 B/G B G 9 90
#3 C/H C H 11 110
#4 D/I D I 13 130
#5 E/J E J 15 150

Answer 2

You can use my package safejoin if it's acceptable to you to use a github package.
The idea is that you have conflicting columns, dplyr and base R deal with conflict by renaming them while safejoin is more flexible, you can use the function you want to apply in case of conflicts. Here you want to add them so we'll use conflict = `+`, for the same effect you could have used conflict = ~ .x + .y or conflict = ~ ..1 + ..2.
# remotes::install_github("moodymudskipper/safejoin")
library(tidyverse)
library(safejoin)
values <- tibble(
id = LETTERS[1:10],
variable1 = 1:10,
variable2 = (1:10)*10
)
df <- tibble(
twin_id = c("A/F", "B/G", "C/H", "D/I", "E/J")
)
joined_df <- df %>%
tidyr::separate(col = twin_id, into = c("left_id", "right_id"), sep = "/", remove = FALSE) %>%
left_join(values, by = c("left_id" = "id")) %>%
safe_left_join(values, by = c("right_id" = "id"), conflict = `+`)
joined_df
#> # A tibble: 5 x 5
#> twin_id left_id right_id variable1 variable2
#> <chr> <chr> <chr> <int> <dbl>
#> 1 A/F A F 7 70
#> 2 B/G B G 9 90
#> 3 C/H C H 11 110
#> 4 D/I D I 13 130
#> 5 E/J E J 15 150
Created on 2020-04-29 by the reprex package (v0.3.0)