creating adjacency network matrix (or list) from large csv dataset using igraph

Question

i am trying to do network analysis in igraph but having some issues with transforming the dataset I have into an edge list (with weights), given the differing amount of columns.

The data set looks as follows (much larger of course): First is the main operator id (main operator can also be partner and vice versa, so the Ids are staying the same in the adjacency) The challenge is that the amount of partners varies (from 0 to 40).

IdMain IdPartner1  IdPartner2  IdPartner3 IdPartner4 .....
1      4           3           2          NA
2      3           1          NA          NA
3      1           4           7          6
4      9           6           3          NA
.
.

my question is how to transform this into an edge list with weight which is undirected (just expressing interaction):

Id1 Id2 weight
1   2    2
1   3    2
1   4    1
2   3    1    
3   4    2
.   .

Does anyone have a tip what the best way to go is? Many thanks in advance!

Answer 1

This is a classic reshaping task. You can use the reshape2 package for this.

text <- "IdMain IdPartner1  IdPartner2  IdPartner3 IdPartner4
1      4           3           2          NA
2      3           NA          NA         NA
3      1           4           7          6
4      9           NA          NA         NA"

data <- read.delim(text = text, sep = "")

library(reshape2)
data_melt <- reshape2::melt(data, id.vars = "IdMain")
edgelist <- data_melt[!is.na(data_melt$value), c("IdMain", "value")]

head(edgelist, 4)
#   IdMain value
# 1      1     4
# 2      2     3
# 3      3     1
# 4      4     9