Binary relation finding the transitive closure












1












$begingroup$


Let $A={a,b,c}$ and the relation given by the following matrix: $mathcal M_r=begin{pmatrix}1&0&1\0&1&0\1&1&0end{pmatrix}$



The task is to find the smallest transitive relation $E$ such that $rsubseteq E$. Which is equivalent of saying find the transitive closure of $r$.



so what I know is that: $t(r)=cup_{ngeq0}r^n, r^n=rcirc rcirc rcirc...circ r, n$ times.



so $mathcal M_{t(r)}=sum_{ninmathbb{N}}mathcal (M_r)^n$ and this gives me $$mathcal M_{t(r)}=begin{pmatrix}1&1&1\0&1&0\1&1&1end{pmatrix}$$



Is there something wrong in my approach?










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$endgroup$












  • $begingroup$
    It's not clear how do you calculate $mathcal M_r^n$ and their sum?
    $endgroup$
    – Berci
    Jan 18 at 14:28












  • $begingroup$
    @Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
    $endgroup$
    – C. Cristi
    Jan 18 at 14:41












  • $begingroup$
    The result is correct. For this specific small example there's a shorter way to solve, though.
    $endgroup$
    – Berci
    Jan 18 at 14:45










  • $begingroup$
    @Berci Which way?
    $endgroup$
    – C. Cristi
    Jan 18 at 14:45
















1












$begingroup$


Let $A={a,b,c}$ and the relation given by the following matrix: $mathcal M_r=begin{pmatrix}1&0&1\0&1&0\1&1&0end{pmatrix}$



The task is to find the smallest transitive relation $E$ such that $rsubseteq E$. Which is equivalent of saying find the transitive closure of $r$.



so what I know is that: $t(r)=cup_{ngeq0}r^n, r^n=rcirc rcirc rcirc...circ r, n$ times.



so $mathcal M_{t(r)}=sum_{ninmathbb{N}}mathcal (M_r)^n$ and this gives me $$mathcal M_{t(r)}=begin{pmatrix}1&1&1\0&1&0\1&1&1end{pmatrix}$$



Is there something wrong in my approach?










share|cite|improve this question











$endgroup$












  • $begingroup$
    It's not clear how do you calculate $mathcal M_r^n$ and their sum?
    $endgroup$
    – Berci
    Jan 18 at 14:28












  • $begingroup$
    @Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
    $endgroup$
    – C. Cristi
    Jan 18 at 14:41












  • $begingroup$
    The result is correct. For this specific small example there's a shorter way to solve, though.
    $endgroup$
    – Berci
    Jan 18 at 14:45










  • $begingroup$
    @Berci Which way?
    $endgroup$
    – C. Cristi
    Jan 18 at 14:45














1












1








1





$begingroup$


Let $A={a,b,c}$ and the relation given by the following matrix: $mathcal M_r=begin{pmatrix}1&0&1\0&1&0\1&1&0end{pmatrix}$



The task is to find the smallest transitive relation $E$ such that $rsubseteq E$. Which is equivalent of saying find the transitive closure of $r$.



so what I know is that: $t(r)=cup_{ngeq0}r^n, r^n=rcirc rcirc rcirc...circ r, n$ times.



so $mathcal M_{t(r)}=sum_{ninmathbb{N}}mathcal (M_r)^n$ and this gives me $$mathcal M_{t(r)}=begin{pmatrix}1&1&1\0&1&0\1&1&1end{pmatrix}$$



Is there something wrong in my approach?










share|cite|improve this question











$endgroup$




Let $A={a,b,c}$ and the relation given by the following matrix: $mathcal M_r=begin{pmatrix}1&0&1\0&1&0\1&1&0end{pmatrix}$



The task is to find the smallest transitive relation $E$ such that $rsubseteq E$. Which is equivalent of saying find the transitive closure of $r$.



so what I know is that: $t(r)=cup_{ngeq0}r^n, r^n=rcirc rcirc rcirc...circ r, n$ times.



so $mathcal M_{t(r)}=sum_{ninmathbb{N}}mathcal (M_r)^n$ and this gives me $$mathcal M_{t(r)}=begin{pmatrix}1&1&1\0&1&0\1&1&1end{pmatrix}$$



Is there something wrong in my approach?







relations binary






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 18 at 19:21









Kevin Long

3,58121431




3,58121431










asked Jan 18 at 13:50









C. CristiC. Cristi

1,655318




1,655318












  • $begingroup$
    It's not clear how do you calculate $mathcal M_r^n$ and their sum?
    $endgroup$
    – Berci
    Jan 18 at 14:28












  • $begingroup$
    @Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
    $endgroup$
    – C. Cristi
    Jan 18 at 14:41












  • $begingroup$
    The result is correct. For this specific small example there's a shorter way to solve, though.
    $endgroup$
    – Berci
    Jan 18 at 14:45










  • $begingroup$
    @Berci Which way?
    $endgroup$
    – C. Cristi
    Jan 18 at 14:45


















  • $begingroup$
    It's not clear how do you calculate $mathcal M_r^n$ and their sum?
    $endgroup$
    – Berci
    Jan 18 at 14:28












  • $begingroup$
    @Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
    $endgroup$
    – C. Cristi
    Jan 18 at 14:41












  • $begingroup$
    The result is correct. For this specific small example there's a shorter way to solve, though.
    $endgroup$
    – Berci
    Jan 18 at 14:45










  • $begingroup$
    @Berci Which way?
    $endgroup$
    – C. Cristi
    Jan 18 at 14:45
















$begingroup$
It's not clear how do you calculate $mathcal M_r^n$ and their sum?
$endgroup$
– Berci
Jan 18 at 14:28






$begingroup$
It's not clear how do you calculate $mathcal M_r^n$ and their sum?
$endgroup$
– Berci
Jan 18 at 14:28














$begingroup$
@Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
$endgroup$
– C. Cristi
Jan 18 at 14:41






$begingroup$
@Berci Using logic operators, $+$ is denoted as OR and $.$ is denoted as AND. And $n$ is the cardinal of set $A$
$endgroup$
– C. Cristi
Jan 18 at 14:41














$begingroup$
The result is correct. For this specific small example there's a shorter way to solve, though.
$endgroup$
– Berci
Jan 18 at 14:45




$begingroup$
The result is correct. For this specific small example there's a shorter way to solve, though.
$endgroup$
– Berci
Jan 18 at 14:45












$begingroup$
@Berci Which way?
$endgroup$
– C. Cristi
Jan 18 at 14:45




$begingroup$
@Berci Which way?
$endgroup$
– C. Cristi
Jan 18 at 14:45










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$begingroup$

Your solution is correct



If our graph is small like this, we can simply draw it (loops at $a$ and $b$ and arrows $ato c, bto c, cto a$), and then use that we have an arrow $xto y$ in the transitive closure iff there is a path $xleadsto y$ in the original graph.






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    $begingroup$

    Your solution is correct



    If our graph is small like this, we can simply draw it (loops at $a$ and $b$ and arrows $ato c, bto c, cto a$), and then use that we have an arrow $xto y$ in the transitive closure iff there is a path $xleadsto y$ in the original graph.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Your solution is correct



      If our graph is small like this, we can simply draw it (loops at $a$ and $b$ and arrows $ato c, bto c, cto a$), and then use that we have an arrow $xto y$ in the transitive closure iff there is a path $xleadsto y$ in the original graph.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Your solution is correct



        If our graph is small like this, we can simply draw it (loops at $a$ and $b$ and arrows $ato c, bto c, cto a$), and then use that we have an arrow $xto y$ in the transitive closure iff there is a path $xleadsto y$ in the original graph.






        share|cite|improve this answer









        $endgroup$



        Your solution is correct



        If our graph is small like this, we can simply draw it (loops at $a$ and $b$ and arrows $ato c, bto c, cto a$), and then use that we have an arrow $xto y$ in the transitive closure iff there is a path $xleadsto y$ in the original graph.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 18 at 18:37









        BerciBerci

        62k23776




        62k23776






























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