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

[Gábor Csárdi]

Hi,

you can actually assign the bucket attributes all at once, and this is
relatively fast, the graph is only copied once.

## Some example data
g <- degree.sequence.game(sample(2:10), method="simple")
buckets <- letters[seq_len(vcount(g))]

## Assign buckets
V(g)$bucket[order(degree(g), decreasing=TRUE)] <- buckets

## Check result
V(g)$bucket

## This gives the same solution as your function:
V(foo(g, buckets))$bucket

Gabor

On Mon, 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
>
>
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-- 
Gabor Csardi <address@hidden>     MTA KFKI RMKI