Re: [igraph] Sorting a graph or assigning attributes based on vertex names

[Tamás Nepusz]

Hi,

First I would try replacing set.vertex.attribute(g, "bucket", vid, bv[i]) with:

V(g)$bucket[vid] <- bv[i]

I think this avoids copying the graph. Also, I would even try this (not sure if 
it works, but it's worth a try):

V(g)$bucket[sortedVertexIDs] <- bv

This would apply all the bucket vectors at once.

-- 
T.

On 29 Oct 2012, at 19:45, Alan Labouseur <address@hidden> wrote:

> Hi. I'm trying to assign a "bucket" attribute (from a vector of buckets) to 
> each vertex based on the position of the vertex degree when sorted. My 
> initial approach seems to work nicely up to the point of setting all of the 
> vertex attributes in the graph. After replicating the bucket vector so that 
> it's long enough to cover all of the vertices in g, I preserve g's vertex IDs 
> in the "name" attribute. Then I sort the vertices based on their degree. Then 
> I take only the "names" portion of the sorted vector which represents the 
> vertex IDs in the order I want to match them up to the buckets vector (bv). 
> But from that point it's horribly slow because of that for loop and 
> constantly reassigning the entire graph (g) after each set.vertex.attribute. 
> I bet there's a better way. I appreciate any help or ideas. Thanks. Here's 
> the code:
> 
> foo <- function(g, buckets) {
>   # REPlicate buckets so that it's long enough to cover all the vertices in g.
>   bv <- rep(buckets, (vcount(g) %/% length(buckets))+1)
>   #
>   # Label each vertex with its current id. 
>   V(g)$name <- V(g)                                              # 
> V(g)[1:20]$name
>   # Sort on degree.
>   sortedDegrees <- sort(degree(g), decreasing=TRUE)              # 
> sortedDegrees[1:20]   
>   # Get the vertices in degree-sorted order.
>   sortedVertexIDs <- attr(sortedDegrees, "names", exact=TRUE)    # 
> sortedVertexIDs[1:20]
>   #
>   # Set the "bucket" attribute of every (sorted) vertex in g to the 
> corresponding (replicated) value in the bv. 
>   i <- 1
>   for (vid in sortedVertexIDs) {
>      g <- set.vertex.attribute(g, "bucket", vid, bv[i])
>      i <- i + 1
>   }
>   #
>   # Return the entire graph.
>   g
> }
> 
> Thanks!
> -Alan
> 
> 
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