R help - Jul 2010 - send out put to file in R

Hi

I am using igraph package in R. 
My goal is to read  a network (in "pajek" format) and decompose the
network
into components.
In addition, I am also interested in sending this output to to a file.

I am having problem in while writing to a file!

my code looks like this
g <- read.graph ("F://test.net", "pajek")
compo <- decompose.graph(g,  mode="weak", max.comps=NA,
min.vertices= 20)
write.graph (compo, "F://new", "pajek")

The error message shown up was -- "Not a Graph Object"

Could any one explain what is the problem here ?

Thanks
chakri  
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On 2010-07-14 4:04, chakri_amateur wrote:
>
> Hi
>
> I am using igraph package in R.
> My goal is to read  a network (in "pajek" format) and decompose
the network
> into components.
> In addition, I am also interested in sending this output to to a file.
>
> I am having problem in while writing to a file!
>
> my code looks like this
> g<- read.graph ("F://test.net", "pajek")
> compo<- decompose.graph(g,  mode="weak", max.comps=NA,
min.vertices= 20)
> write.graph (compo, "F://new", "pajek")
>
> The error message shown up was -- "Not a Graph Object"
>
> Could any one explain what is the problem here ?
Sure: compo is not an igraph object; it's a list as
class(compo) or reading the help page for decompose.graph
would tell you.

   -Peter Ehlers
>
> Thanks
> chakri

On Thu, Jul 15, 2010 at 6:38 PM, chakri_amateur <chakri2sai at
yahoo.co.in> wrote:
[...]
> I want to extract the largest connected component (alias sub-graph) of the
> network. My input network is a large network of >1000 vertices and
>15000
> arcs. From this, I want to take out only the largest cluster.
>
>> If you decompose a graph to components, you get a list of graphs;
>
> Yes. But I want only the largest sub-graph. It is first in the list
> sub-graphs generated. Am I right ? I tried with 10 files, and all the time
> the largest sub-graph is shown first in the list. (i.e i=1, in compo[[i]])
No, this is not right. It is just a coincidence. The components are
not ordered. In fact, the first component in the list is the one that
has the first (well, zeroth) vertex. Check the sizes of the components
and explicitly choose the largest one:

compo[[ which.max(sapply(compo, vcount)) ]]

Best,
Gabor
>> for (i in seq_along(compo)) {
>> ? write.graph(compo[[i]], file=paste(sep="",
"new-", i, ".net"),
>> format="pajek")
>> }
>
> It worked. I Just had to give entire file path instead of just
"new" !
>
> for (i in seq_along(compo)) {
> write.graph(compo[[i]], file=paste(sep="", "F://new-",
i, ".net"), "pajek")
> }
>
> or For the first component
> write.graph(compo[[1]], "F://new.net", "pajek")
>
> Chakri
>
>
>
>
> Second,
> --
> View this message in context:
http://r.789695.n4.nabble.com/send-out-put-to-file-in-R-tp2288515p2290393.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Gabor Csardi <Gabor.Csardi at unil.ch>? ?? UNIL DGM