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

[Alan Labouseur]

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

... did indeed work, once I as.integer'd the sortedVertexIDs. 

Thanks Tamás, that was a great help.

-Alan

> On Tue, Oct 30, 2012 at 6:18 PM, Tamás Nepusz <address@hidden> wrote:
> > Hi,
> >
> > First I would try replacing set.vertex.attribute(g, "bucket", vid, bv[i]) 
> > with:
> >
> > V(g)$bucket[vid] <- bv[i]
> >
> > I think this avoids copying the graph. Also, I would even try this (not 
> > sure 
> > if it works, but it's worth a try):
> 
> Just to avoid mistakes in the archives. This also copies the graph. It
> is stupid, but it does. It is very hard to modify objects in place in
> R.
> 
> > V(g)$bucket[sortedVertexIDs] <- bv
> 
> This might work, but only if your vertex names are numbers from one to
> number-of-vertices, I believe.
> 
> Gabor
> 
> [...]

> On Oct 29, 2012, at 2:45 PM, 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
>> 
>