Measure of subgraph isomorphisms












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I have a "big" (biological) finite graph $Gamma = (V, E)$ and a set of subsets of vertices $S = {gamma(t)}_{t in mathcal T}$ (with a given function $gamma : mathcal T to mathcal P(V)$ where $|V| simeq 18,000$ and $|mathcal T| simeq 12,500$). I am interested in the different subgraphs induced by the $gamma(t)$ modulo isomorphisms. I claim that in my case, the number of different non-isomorphic subgraphs is clearly higher than expected if they were uniformly distributed among $V$. To do this, I sample uniformly selected subsets of $V$ (of the same size as the $gamma(t)$ subsets) and look at the number of non-isomorphic subgraphs I end up with, and then repeat this step a lot of times to have an idea of the distribution of the number of non-isomorphic subgraphs under the uniform sampling.



However I need to have a statistical measure on this. So what I did was approximating the probability distribution mentioned right above and use Chebyshev's inequality to infer an upper bound that is used as a $p$-value. This gives me what I expect (i.e. a very low $p$-value).



My first question is: is this method valid in any way? and my second question is: how can I measure the "density" of isomorphisms?



What I mean by "density of isomorphisms" is a scalar value (hopefully normalized so between 0 and 1) that will represent somehow how much of isomorphisms can be found within my subgraphs. The only thing I have been able to come up with so far is based on Shannon entropy (yeah computer science background here):



$$H(S) = frac 1{log |S|}sum_{s in S/simeq}frac {|s|}{|S|}logfrac {|s|}{|S|},$$



where $S/simeq$ is the set of isomorphism classes and $frac 1{log |S|}$ is there to normalize the value. But again I have no idea if this can get me somewhere in the statistical analysis of my results.










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    1












    $begingroup$


    I have a "big" (biological) finite graph $Gamma = (V, E)$ and a set of subsets of vertices $S = {gamma(t)}_{t in mathcal T}$ (with a given function $gamma : mathcal T to mathcal P(V)$ where $|V| simeq 18,000$ and $|mathcal T| simeq 12,500$). I am interested in the different subgraphs induced by the $gamma(t)$ modulo isomorphisms. I claim that in my case, the number of different non-isomorphic subgraphs is clearly higher than expected if they were uniformly distributed among $V$. To do this, I sample uniformly selected subsets of $V$ (of the same size as the $gamma(t)$ subsets) and look at the number of non-isomorphic subgraphs I end up with, and then repeat this step a lot of times to have an idea of the distribution of the number of non-isomorphic subgraphs under the uniform sampling.



    However I need to have a statistical measure on this. So what I did was approximating the probability distribution mentioned right above and use Chebyshev's inequality to infer an upper bound that is used as a $p$-value. This gives me what I expect (i.e. a very low $p$-value).



    My first question is: is this method valid in any way? and my second question is: how can I measure the "density" of isomorphisms?



    What I mean by "density of isomorphisms" is a scalar value (hopefully normalized so between 0 and 1) that will represent somehow how much of isomorphisms can be found within my subgraphs. The only thing I have been able to come up with so far is based on Shannon entropy (yeah computer science background here):



    $$H(S) = frac 1{log |S|}sum_{s in S/simeq}frac {|s|}{|S|}logfrac {|s|}{|S|},$$



    where $S/simeq$ is the set of isomorphism classes and $frac 1{log |S|}$ is there to normalize the value. But again I have no idea if this can get me somewhere in the statistical analysis of my results.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I have a "big" (biological) finite graph $Gamma = (V, E)$ and a set of subsets of vertices $S = {gamma(t)}_{t in mathcal T}$ (with a given function $gamma : mathcal T to mathcal P(V)$ where $|V| simeq 18,000$ and $|mathcal T| simeq 12,500$). I am interested in the different subgraphs induced by the $gamma(t)$ modulo isomorphisms. I claim that in my case, the number of different non-isomorphic subgraphs is clearly higher than expected if they were uniformly distributed among $V$. To do this, I sample uniformly selected subsets of $V$ (of the same size as the $gamma(t)$ subsets) and look at the number of non-isomorphic subgraphs I end up with, and then repeat this step a lot of times to have an idea of the distribution of the number of non-isomorphic subgraphs under the uniform sampling.



      However I need to have a statistical measure on this. So what I did was approximating the probability distribution mentioned right above and use Chebyshev's inequality to infer an upper bound that is used as a $p$-value. This gives me what I expect (i.e. a very low $p$-value).



      My first question is: is this method valid in any way? and my second question is: how can I measure the "density" of isomorphisms?



      What I mean by "density of isomorphisms" is a scalar value (hopefully normalized so between 0 and 1) that will represent somehow how much of isomorphisms can be found within my subgraphs. The only thing I have been able to come up with so far is based on Shannon entropy (yeah computer science background here):



      $$H(S) = frac 1{log |S|}sum_{s in S/simeq}frac {|s|}{|S|}logfrac {|s|}{|S|},$$



      where $S/simeq$ is the set of isomorphism classes and $frac 1{log |S|}$ is there to normalize the value. But again I have no idea if this can get me somewhere in the statistical analysis of my results.










      share|cite|improve this question











      $endgroup$




      I have a "big" (biological) finite graph $Gamma = (V, E)$ and a set of subsets of vertices $S = {gamma(t)}_{t in mathcal T}$ (with a given function $gamma : mathcal T to mathcal P(V)$ where $|V| simeq 18,000$ and $|mathcal T| simeq 12,500$). I am interested in the different subgraphs induced by the $gamma(t)$ modulo isomorphisms. I claim that in my case, the number of different non-isomorphic subgraphs is clearly higher than expected if they were uniformly distributed among $V$. To do this, I sample uniformly selected subsets of $V$ (of the same size as the $gamma(t)$ subsets) and look at the number of non-isomorphic subgraphs I end up with, and then repeat this step a lot of times to have an idea of the distribution of the number of non-isomorphic subgraphs under the uniform sampling.



      However I need to have a statistical measure on this. So what I did was approximating the probability distribution mentioned right above and use Chebyshev's inequality to infer an upper bound that is used as a $p$-value. This gives me what I expect (i.e. a very low $p$-value).



      My first question is: is this method valid in any way? and my second question is: how can I measure the "density" of isomorphisms?



      What I mean by "density of isomorphisms" is a scalar value (hopefully normalized so between 0 and 1) that will represent somehow how much of isomorphisms can be found within my subgraphs. The only thing I have been able to come up with so far is based on Shannon entropy (yeah computer science background here):



      $$H(S) = frac 1{log |S|}sum_{s in S/simeq}frac {|s|}{|S|}logfrac {|s|}{|S|},$$



      where $S/simeq$ is the set of isomorphism classes and $frac 1{log |S|}$ is there to normalize the value. But again I have no idea if this can get me somewhere in the statistical analysis of my results.







      graph-theory graph-isomorphism






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      edited Jan 9 at 22:49







      Bermudes

















      asked Jan 8 at 13:12









      BermudesBermudes

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