R - Function that call conditionally another functions - r

Question

I am working with igraph package and I'm trying to build a function that calculates the number of intra-community edges of different algorithm implementation. I try to concatenate everything inside the function even the algorithms community detection functions. Like this:
library("igraph")
intra.edges<-function(G,algorithm) {
if(algorithm==1){
Mod<-cluster_louvain(G)}
if(algoritmo==2){
Mod<-cluster_edge_betweenness(G)}
if(algoritmo==3){
Mod<-cluster_walktrap(G)}
Com<-as.data.frame(sizes(Mod))
NoCom<-as.vector(Com$Community.sizes)
vert<-NULL
for(i in 1:length(NoCom)){
M<-which(membership(Mod)==i)
sg<-induced.subgraph(G,M)
c.ec<-ecount(sg)
vert<-c.ec
}
intra<-data.frame(Com,vert)
print(intra)
}
When I try the function, it don't works correctly. For example:
When I run:
G <- graph.famous("Zachary")
intra.edges(G,1)
I get:
Community.sizes Freq vert
1 9 6
2 7 6
3 9 6
4 4 6
5 5 6
And when I run intra.edges(G,2) or intra.edges(G,3) I get the same output.
Also, not all the network's components have six vertex, it is only in one component.

Answer 1

You can either add your calculated value of vert to the dataframe with each iteration of your for loop by changing your code to:
intra<-Com
for(i in 1:length(NoCom)){
M<-which(membership(Mod)==i)
sg<-induced.subgraph(G,M)
intra$vert[i]<-ecount(sg)
}
print(intra)
Or, as #dash2 suggested, create a vector called vert and add values sequentially like this:
vert<-NULL
for(i in 1:length(NoCom)){
M<-which(membership(Mod)==i)
sg<-induced.subgraph(G,M)
c.ec<-ecount(sg)
vert[i]<-c.ec
}