Re: [igraph] edge.betweenness returns negative or NaN values

[Tamas Nepusz]

Ah, my bad, I did not notice that you meant the edge betweenness and
not the node betweenness. It looks like the edge betweenness related
code does not include a similar bigint workaround. This should be
fixed in the next version then - can you add a bug report to
https://github.com/igraph/igraph/issues ?

Thanks,
T.

T.


On Sun, Sep 13, 2015 at 9:24 AM, Vincent Labatut
<address@hidden> wrote:
> Hello Tamas,
>
> and thanks for your answer.
> I was thinking of something like that, since the networks are lattices and
> this case is mentionned in the documentation.
> I also had noticed the "nobigint" parameter for the "betweenness" functions,
> however it does not exist for the "edge.betweenness" functions.
> Best,
> Vincent
>
>> Hello,
>>
>> The negative values are most likely due to integer overflows (i.e. the
>> betweenness score would be too large and the underlying variable in
>> which igraph computes the betweenness score overflows). You can get
>> around this by passing nobigint=FALSE to the edge betweenness call -
>> it will make igraph use "big integers", which can hold arbitrarily
>> large numbers at the expense of being somewhat slower.
>>
>> As for the NaNs, it could be a bug, but let's see first whether the
>> issue persists with nobigint=FALSE. If so, let us know and try to post
>> a small example on which we could reproduce the issue with NaNs.
>>
>> T.
>>
>>
>>
>> On Sat, Sep 12, 2015 at 3:08 PM, Vincent Labatut
>> <address@hidden> wrote:
>>> Hello,
>>>
>>> I am processing the edge-betweenness of various networks using R igraph
>>> version 7.1. Those are spatial networks (each node has a (x,y) position)
>>> and
>>> I am using the "weight" option of the "edge.betweenness" function to take
>>> the spatial distances into account. This spatial distance is stored in an
>>> edge attribute called "dist".
>>>
>>> Here is the command I use:
>>> edge.betweenness(graph=g, weights=E(g)$dist)
>>>
>>> However, for some of my networks, I get negative values, or even NaN.
>>> Here
>>> are two examples, under the graphml format:
>>> http://dx.doi.org/10.6084/m9.figshare.1540708
>>> - scale=32.graphml
>>> - scale=41.graphml
>>>
>>> For the first one, the first values returned by "edge.betweenness" are:
>>>    [1] 1904887544.08 1904887544.08 1896303182.39 1951787568.72
>>> 1203043060.76
>>>    [6] 1270869072.68  622780616.09  667964773.27  279064394.68
>>> 309184936.21
>>>   [11]  135403467.81  155266075.94   51600202.02   60120695.31
>>> 21113003.39
>>>   [16]   24783603.89    6275147.30    6937885.52    1347425.01
>>> 1002544.99
>>>   [21]     150574.42    -327097.77    -711849.38   -1430744.36
>>> -246214.20
>>>   [26]    -602827.15    -230344.97    -484630.12    -297768.08
>>> -492364.06
>>>
>>> For the second one, all the returned values are NaN.
>>>
>>> Note that all these weights are positive by definition. They even are
>>> non-zero since no two nodes hold the same position, by construction. I
>>> also
>>> checked this programmatically. Moreover, there are no multiple links,
>>> also
>>> by construction (and I checked with "has.multiple").
>>>
>>> I was wondering if the negative or NaN values I get are due to me
>>> misusing
>>> the function, or if this is a bug in igraph.
>>>
>>> Thanks,
>>> Vincent Labatut
>>>
>>> _______________________________________________
>>> igraph-help mailing list
>>> address@hidden
>>> https://lists.nongnu.org/mailman/listinfo/igraph-help
>>>
>
>
> On Sat, Sep 12, 2015 at 3:08 PM, Vincent Labatut <address@hidden>
> wrote:
>>
>> Hello,
>>
>> I am processing the edge-betweenness of various networks using R igraph
>> version 7.1. Those are spatial networks (each node has a (x,y) position) and
>> I am using the "weight" option of the "edge.betweenness" function to take
>> the spatial distances into account. This spatial distance is stored in an
>> edge attribute called "dist".
>>
>> Here is the command I use:
>> edge.betweenness(graph=g, weights=E(g)$dist)
>>
>> However, for some of my networks, I get negative values, or even NaN. Here
>> are two examples, under the graphml format:
>> http://dx.doi.org/10.6084/m9.figshare.1540708
>> - scale=32.graphml
>> - scale=41.graphml
>>
>> For the first one, the first values returned by "edge.betweenness" are:
>>    [1] 1904887544.08 1904887544.08 1896303182.39 1951787568.72
>> 1203043060.76
>>    [6] 1270869072.68  622780616.09  667964773.27  279064394.68
>> 309184936.21
>>   [11]  135403467.81  155266075.94   51600202.02   60120695.31
>> 21113003.39
>>   [16]   24783603.89    6275147.30    6937885.52    1347425.01
>> 1002544.99
>>   [21]     150574.42    -327097.77    -711849.38   -1430744.36
>> -246214.20
>>   [26]    -602827.15    -230344.97    -484630.12    -297768.08
>> -492364.06
>>
>> For the second one, all the returned values are NaN.
>>
>> Note that all these weights are positive by definition. They even are
>> non-zero since no two nodes hold the same position, by construction. I also
>> checked this programmatically. Moreover, there are no multiple links, also
>> by construction (and I checked with "has.multiple").
>>
>> I was wondering if the negative or NaN values I get are due to me misusing
>> the function, or if this is a bug in igraph.
>>
>> Thanks,
>> Vincent Labatut
>
>
>
> _______________________________________________
> igraph-help mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/igraph-help
>