Re: [igraph] (no subject)

[Belavenutti Martins da Silva, Pedro]

I am working from R. I am trying to implement this call back function in R but it seems to do not work.

Here in an example:

library(igraph)

d<-matrix(c(1, 0, 0, 0, 0.9,   

            0, 1, 0.6, 0.4, 0.5,  

            0, 0.6, 1, 0, 0.8,  

            0, 0.4, 0, 1, 0.5,  

            0.9, 0.5, 0.8, 0.5, 1), byrow=T, nrow=5)    

g<-graph.adjacency(d, weighted=T, mode="lower",diag=FALSE, add.colnames=NA)

plot(g)

threshold-value <- 2 #Whow to use this information in the process?

dfs <- dfs(g, root = 1 ) #ex: I do not know any method to set up a threshold-value n in here to stop the function.

visited <-  dfs$order

Sum_Weights <- sum(E(g)$weight[visited])# here the Sum_Weights should be the threshold-value  

##################

## Terminate after the threshold-value , using a callback

threshold-value <- 2

data1 <- E(g)$weight

f.out <- function(graph, data1, extra) {

  

  edge <- data['vid']

  

  sum <- unlist(append(sum, data1[edge]))

  

  sum >  threshold-value

}

dfs <- dfs(g, root = 1,out.callback=f.out) # it does not work and aborts the current R section.

---

From: igraph-help [igraph-help-bounces+pedro.belavenutti=address@hidden] on behalf of Tamas Nepusz [address@hidden]
Sent: Tuesday, March 10, 2020 9:29 AM
To: Help for igraph users
Subject: Re: [igraph] (no subject)

So I need to use the  Deep First Search algorithm from a random node and stop the algorithm when the sum of node or vertices weights in the DFS sub-graph achieve a certain limit.

Could you please help me telling if it is possible with the dfs igraph function?

Are you working from C? If so, you can use the "in_callback" and "out_callback" arguments of igraph_dfs to call arbitrary functions when the DFS starts visiting a node or when the DFS is done with a node and its subgraph. You can also return a non-zero value from the callback functions to request igraph to terminate the search.

Documentation here:

https://igraph.org/c/doc/igraph-Visitors.html#igraph_dfs

https://igraph.org/c/doc/igraph-Visitors.html#igraph_dfshandler_t

T.