Merge two datasets - r

Question

I create a node list as follows:
name <- c("Joe","Frank","Peter")
city <- c("New York","Detroit","Maimi")
age <- c(24,55,65)
node_list <- data.frame(name,age,city)
node_list
name age city
1 Joe 24 New York
2 Frank 55 Detroit
3 Peter 65 Maimi
Then I create an edge list as follows:
from <- c("Joe","Frank","Peter","Albert")
to <- c("Frank","Albert","James","Tony")
to_city <- c("Detroit","St. Louis","New York","Carson City")
edge_list <- data.frame(from,to,to_city)
edge_list
from to to_city
1 Joe Frank Detroit
2 Frank Albert St. Louis
3 Peter James New York
4 Albert Tony Carson City
Notice that the names in the node list and edge list do not overlap 100%. I want to create a master node list of all the names, capturing city information as well. This is my dplyr attempt to do this:
new_node <- edge_list %>%
gather("from_to", "name", from, to) %>%
distinct(name) %>%
full_join(node_list)
new_node
name age city
1 Joe 24 New York
2 Frank 55 Detroit
3 Peter 65 Maimi
4 Albert NA <NA>
5 James NA <NA>
6 Tony NA <NA>
I need to figure out how to add to_city information. What do I need to add to my dplyr code to make this happen? Thanks.

Answer 1

Join twice, once on to and once on from, with the irrelevant columns subsetted out:
library(dplyr)
node_list <- data_frame(name = c("Joe", "Frank", "Peter"),
city = c("New York", "Detroit", "Maimi"),
age = c(24, 55, 65))
edge_list <- data_frame(from = c("Joe", "Frank", "Peter", "Albert"),
to = c("Frank", "Albert", "James", "Tony"),
to_city = c("Detroit", "St. Louis", "New York", "Carson City"))
node_list %>%
full_join(select(edge_list, name = to, city = to_city)) %>%
full_join(select(edge_list, name = from))
#> Joining, by = c("name", "city")
#> Joining, by = "name"
#> # A tibble: 6 x 3
#> name city age
#> <chr> <chr> <dbl>
#> 1 Joe New York 24.
#> 2 Frank Detroit 55.
#> 3 Peter Maimi 65.
#> 4 Albert St. Louis NA
#> 5 James New York NA
#> 6 Tony Carson City NA
In this case the second join doesn't do anything because everybody is already included, but it would insert anyone who only existed in the from column.