On 14 September 2015 at 00:30, Szabolcs Horvát <[email protected]> wrote: > Just to have a simple test case: > > Based on a comparison with Mathematica, for an n*n grid graph things > start to go wrong at n=35. For n=34 the edge betweenness is still > accurate. >
While the n=34 value is about right for the limits of betweenness calculation without bigints, it happens to be the case that for n > 34 Mathematica also gives bad results (different ones). > On 13 September 2015 at 22:37, Tamas Nepusz <[email protected]> wrote: >> 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 >> <[email protected]> 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 <[email protected]> >>> 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 >>> [email protected] >>> https://lists.nongnu.org/mailman/listinfo/igraph-help >>> >> >> _______________________________________________ >> igraph-help mailing list >> [email protected] >> https://lists.nongnu.org/mailman/listinfo/igraph-help _______________________________________________ igraph-help mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/igraph-help
