How to save an igraph object

Question

I have a problem writing my data frame to csv file.

g looks like this

> g
IGRAPH c32bbbf UN-- 12 12 -- 
+ attr: name (v/c)
+ edges from c32bbbf (vertex names):
 [1] 2 --3  3 --1  4 --5  5 --6  4 --6  6 --7  6 --8  6 --9  9 --8  10--11 11--12 10--12

None of folowing code works

write.table(g,  file = "filename.csv", sep = ";", dec = ",", row.names = FALSE)
write.csv2(membership(cluster_edge_betweenness(g)), "name.csv" , row.names = FALSE)
write.table(membership(cluster_edge_betweenness(g)),  file = "name.csv", sep = ";", dec = ",", row.names = FALSE)

It shows this error

Error in as.data.frame.default(x[[i]], optional = TRUE) : 
  cannot coerce class ‘"membership"’ to a data.frame

How can I write g or membership(cluster_edge_betweenness(g)) into a.csv file? Thanks for help in advance.

Answer 1

Use igraph's write_graph() function. Check the documentation for available formats.

Answer 2

write.table and write.csv require that the input be a tabular data (data.frame/matrix/etc.). Your object g is an igraph object. As others have mentioned, one option is to use igraph's write_graph() function , that will write the graph to a text file and allows different formats for how the data is written.

Another option would be to use igraph's as_long_data_frame function to convert your graph object to a dataframe, which can then be written to a csv file using write.csv . However, this requires that the vertices be named.

For example:

library(igraph)

g <- make_ring(10)

# add names to vertices
vertex_attr(g) <- list(name = LETTERS[1:10])    
vertex_attr(g, "label") <- V(g)$name

as_long_data_frame(g)    

#>  from to from_name from_label to_name to_label
#>     1  2         A          A       B        B
#>     2  3         B          B       C        C
#>     3  4         C          C       D        D
#>     4  5         D          D       E        E
#>     5  6         E          E       F        F
#>     6  7         F          F       G        G
#>     7  8         G          G       H        H
#>     8  9         H          H       I        I
#>     9 10         I          I       J        J
#>     1 10         A          A       J        J