Re: [igraph] shortest path calculation

[Thiago M. Venancio]

Thanks Gabor !
It worked.
My toy file is simple:

#=======
a b
b c
c d
#=======

The interesting point is that the shortest.paths function does not work without assigning the weights=FALSE, but the average.path.length and path.length.hist work without any problems. Since they are related, I was just wondering what is different in how they handle the data.

Best,

Thiago

On Fri, Jan 30, 2009 at 11:40 AM, Gábor Csárdi <address@hidden> wrote:

Hmmm, again I cannot be sure what happens, because I haven't seen your
file. Anyway, giving 'weights=FALSE' to read.graph should solve the
problem.

G.

On Fri, Jan 30, 2009 at 5:37 PM, Thiago M. Venancio

<address@hidden> wrote:
> Hi Gabor,
> You got it right. There is no weight in the file. Assigning one does the
> trick.
> My graph is unweighted, is there any way to assign 1 during the file reading
> or do I have to change the file to include an useless column with ones ?
> Thank you very much.
> Thiago
>
> On Fri, Jan 30, 2009 at 11:33 AM, Gábor Csárdi <address@hidden> wrote:
>>
>> Impossible to tell for sure without knowing what is in the file "b".
>> My guess is that all edges have weight zero, but can be something
>> else.
>>
>> G.
>>
>> On Fri, Jan 30, 2009 at 5:30 PM, Thiago M. Venancio
>> <address@hidden> wrote:
>> > Hi,
>> >
>> > I am experiencing some problems in calculating the shortest path length
>> > matrix. Note that it is giving zeroes for all the cells, even when
>> > vertices
>> > are connected.
>> > I noticed the V() function return indexes in the indexes and in my graph
>> > return quoted numbers. Explicitly telling the indexes also does not
>> > solve
>> > the problem.
>> > The example in the documentation is working. I do not know what is the
>> > problem in my code.
>> > Below is a toy example.
>> >
>> > Thanks.
>> >
>> > Thiago
>> >
>> > test = read.graph("b", format="ncol", names=T)
>> >> test
>> > Vertices: 4
>> > Edges: 3
>> > Directed: FALSE
>> > Edges:
>> >
>> > [0] a -- b
>> > [1] b -- c
>> > [2] c -- d
>> >
>> >> shortest.paths(test)
>> >      [,1] [,2] [,3] [,4]
>> > [1,]    0    0    0    0
>> > [2,]    0    0    0    0
>> > [3,]    0    0    0    0
>> > [4,]    0    0    0    0
>> >
>> >> shortest.paths(test,v=1:2)
>> >      [,1] [,2] [,3] [,4]
>> > [1,]    0    0    0    0
>> > [2,]    0    0    0    0
>> >
>> >
>> >
>> > _______________________________________________
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>> > http://lists.nongnu.org/mailman/listinfo/igraph-help
>> >
>> >
>>
>>
>>
>> --
>> Gabor Csardi <address@hidden>     UNIL DGM
>>
>>
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>
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--
Gabor Csardi <address@hidden>     UNIL DGM


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