how do I check linear independence of m vectors, given the m-1 first vectors are independence?












0












$begingroup$


I have a set of m-1 vectors of size n, they are independence. I want to add another vector and to check if the m vectors are still independence. It is known m < n. I am looking for a good algorithm & running time.
Thanks










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$endgroup$












  • $begingroup$
    I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
    $endgroup$
    – Peter
    Jan 20 at 9:44










  • $begingroup$
    nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
    $endgroup$
    – Shaq
    Jan 20 at 9:46












  • $begingroup$
    Then, determining the rank (as mentioned in my answer) should be a suitable approach.
    $endgroup$
    – Peter
    Jan 20 at 9:48
















0












$begingroup$


I have a set of m-1 vectors of size n, they are independence. I want to add another vector and to check if the m vectors are still independence. It is known m < n. I am looking for a good algorithm & running time.
Thanks










share|cite|improve this question









$endgroup$












  • $begingroup$
    I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
    $endgroup$
    – Peter
    Jan 20 at 9:44










  • $begingroup$
    nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
    $endgroup$
    – Shaq
    Jan 20 at 9:46












  • $begingroup$
    Then, determining the rank (as mentioned in my answer) should be a suitable approach.
    $endgroup$
    – Peter
    Jan 20 at 9:48














0












0








0





$begingroup$


I have a set of m-1 vectors of size n, they are independence. I want to add another vector and to check if the m vectors are still independence. It is known m < n. I am looking for a good algorithm & running time.
Thanks










share|cite|improve this question









$endgroup$




I have a set of m-1 vectors of size n, they are independence. I want to add another vector and to check if the m vectors are still independence. It is known m < n. I am looking for a good algorithm & running time.
Thanks







linear-algebra algorithms






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 20 at 9:15









ShaqShaq

2849




2849












  • $begingroup$
    I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
    $endgroup$
    – Peter
    Jan 20 at 9:44










  • $begingroup$
    nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
    $endgroup$
    – Shaq
    Jan 20 at 9:46












  • $begingroup$
    Then, determining the rank (as mentioned in my answer) should be a suitable approach.
    $endgroup$
    – Peter
    Jan 20 at 9:48


















  • $begingroup$
    I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
    $endgroup$
    – Peter
    Jan 20 at 9:44










  • $begingroup$
    nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
    $endgroup$
    – Shaq
    Jan 20 at 9:46












  • $begingroup$
    Then, determining the rank (as mentioned in my answer) should be a suitable approach.
    $endgroup$
    – Peter
    Jan 20 at 9:48
















$begingroup$
I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
$endgroup$
– Peter
Jan 20 at 9:44




$begingroup$
I guess you want to use the linear independence of the $ m-1 $ vectors for a shortcut. Is that right ?
$endgroup$
– Peter
Jan 20 at 9:44












$begingroup$
nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
$endgroup$
– Shaq
Jan 20 at 9:46






$begingroup$
nope, just it is greater the the number of vectors you have, so you cannot negate it directly.. and yes this is what I am looking for
$endgroup$
– Shaq
Jan 20 at 9:46














$begingroup$
Then, determining the rank (as mentioned in my answer) should be a suitable approach.
$endgroup$
– Peter
Jan 20 at 9:48




$begingroup$
Then, determining the rank (as mentioned in my answer) should be a suitable approach.
$endgroup$
– Peter
Jan 20 at 9:48










2 Answers
2






active

oldest

votes


















0












$begingroup$

You can use the following criterion :



If you have $ m-1 $ linear independent vectors, then adding the $ m $- th vector gives again a linear independent set if and only if the $ m $ - th vector is not a linear-combination of the original $ m-1 $ vectors, in other words there are no real numbers $ a_1,cdots, a_{m-1} $ with $$sum_{j=1}^{m-1} a_jv_j=v_m$$



For the check I suggest to collect the vectors in a matrix and determine the rank.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    How does this help for checking?
    $endgroup$
    – mathreadler
    Jan 20 at 9:31








  • 1




    $begingroup$
    @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
    $endgroup$
    – E-mu
    Jan 20 at 9:33












  • $begingroup$
    Sure it may hint but then maybe it can be good to at least write hint.
    $endgroup$
    – mathreadler
    Jan 20 at 9:36










  • $begingroup$
    Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
    $endgroup$
    – Shaq
    Jan 20 at 9:37






  • 1




    $begingroup$
    @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
    $endgroup$
    – E-mu
    Jan 20 at 10:23





















0












$begingroup$

Project the new vector on the others and remove.



If anything remains afterwards then they are linearly independent.






share|cite|improve this answer









$endgroup$













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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0












    $begingroup$

    You can use the following criterion :



    If you have $ m-1 $ linear independent vectors, then adding the $ m $- th vector gives again a linear independent set if and only if the $ m $ - th vector is not a linear-combination of the original $ m-1 $ vectors, in other words there are no real numbers $ a_1,cdots, a_{m-1} $ with $$sum_{j=1}^{m-1} a_jv_j=v_m$$



    For the check I suggest to collect the vectors in a matrix and determine the rank.






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      How does this help for checking?
      $endgroup$
      – mathreadler
      Jan 20 at 9:31








    • 1




      $begingroup$
      @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
      $endgroup$
      – E-mu
      Jan 20 at 9:33












    • $begingroup$
      Sure it may hint but then maybe it can be good to at least write hint.
      $endgroup$
      – mathreadler
      Jan 20 at 9:36










    • $begingroup$
      Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
      $endgroup$
      – Shaq
      Jan 20 at 9:37






    • 1




      $begingroup$
      @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
      $endgroup$
      – E-mu
      Jan 20 at 10:23


















    0












    $begingroup$

    You can use the following criterion :



    If you have $ m-1 $ linear independent vectors, then adding the $ m $- th vector gives again a linear independent set if and only if the $ m $ - th vector is not a linear-combination of the original $ m-1 $ vectors, in other words there are no real numbers $ a_1,cdots, a_{m-1} $ with $$sum_{j=1}^{m-1} a_jv_j=v_m$$



    For the check I suggest to collect the vectors in a matrix and determine the rank.






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      How does this help for checking?
      $endgroup$
      – mathreadler
      Jan 20 at 9:31








    • 1




      $begingroup$
      @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
      $endgroup$
      – E-mu
      Jan 20 at 9:33












    • $begingroup$
      Sure it may hint but then maybe it can be good to at least write hint.
      $endgroup$
      – mathreadler
      Jan 20 at 9:36










    • $begingroup$
      Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
      $endgroup$
      – Shaq
      Jan 20 at 9:37






    • 1




      $begingroup$
      @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
      $endgroup$
      – E-mu
      Jan 20 at 10:23
















    0












    0








    0





    $begingroup$

    You can use the following criterion :



    If you have $ m-1 $ linear independent vectors, then adding the $ m $- th vector gives again a linear independent set if and only if the $ m $ - th vector is not a linear-combination of the original $ m-1 $ vectors, in other words there are no real numbers $ a_1,cdots, a_{m-1} $ with $$sum_{j=1}^{m-1} a_jv_j=v_m$$



    For the check I suggest to collect the vectors in a matrix and determine the rank.






    share|cite|improve this answer











    $endgroup$



    You can use the following criterion :



    If you have $ m-1 $ linear independent vectors, then adding the $ m $- th vector gives again a linear independent set if and only if the $ m $ - th vector is not a linear-combination of the original $ m-1 $ vectors, in other words there are no real numbers $ a_1,cdots, a_{m-1} $ with $$sum_{j=1}^{m-1} a_jv_j=v_m$$



    For the check I suggest to collect the vectors in a matrix and determine the rank.







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited Jan 20 at 9:38

























    answered Jan 20 at 9:24









    PeterPeter

    47.6k1039131




    47.6k1039131












    • $begingroup$
      How does this help for checking?
      $endgroup$
      – mathreadler
      Jan 20 at 9:31








    • 1




      $begingroup$
      @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
      $endgroup$
      – E-mu
      Jan 20 at 9:33












    • $begingroup$
      Sure it may hint but then maybe it can be good to at least write hint.
      $endgroup$
      – mathreadler
      Jan 20 at 9:36










    • $begingroup$
      Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
      $endgroup$
      – Shaq
      Jan 20 at 9:37






    • 1




      $begingroup$
      @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
      $endgroup$
      – E-mu
      Jan 20 at 10:23




















    • $begingroup$
      How does this help for checking?
      $endgroup$
      – mathreadler
      Jan 20 at 9:31








    • 1




      $begingroup$
      @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
      $endgroup$
      – E-mu
      Jan 20 at 9:33












    • $begingroup$
      Sure it may hint but then maybe it can be good to at least write hint.
      $endgroup$
      – mathreadler
      Jan 20 at 9:36










    • $begingroup$
      Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
      $endgroup$
      – Shaq
      Jan 20 at 9:37






    • 1




      $begingroup$
      @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
      $endgroup$
      – E-mu
      Jan 20 at 10:23


















    $begingroup$
    How does this help for checking?
    $endgroup$
    – mathreadler
    Jan 20 at 9:31






    $begingroup$
    How does this help for checking?
    $endgroup$
    – mathreadler
    Jan 20 at 9:31






    1




    1




    $begingroup$
    @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
    $endgroup$
    – E-mu
    Jan 20 at 9:33






    $begingroup$
    @mathreadler It hints at setting up a matrix equation which can be used as a check, at least that's what I gathered.
    $endgroup$
    – E-mu
    Jan 20 at 9:33














    $begingroup$
    Sure it may hint but then maybe it can be good to at least write hint.
    $endgroup$
    – mathreadler
    Jan 20 at 9:36




    $begingroup$
    Sure it may hint but then maybe it can be good to at least write hint.
    $endgroup$
    – mathreadler
    Jan 20 at 9:36












    $begingroup$
    Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
    $endgroup$
    – Shaq
    Jan 20 at 9:37




    $begingroup$
    Thanks, I got the theory. I am asking how to do it, I mean how do you check it? What kind of algorithm and hat would be the run time complexity?
    $endgroup$
    – Shaq
    Jan 20 at 9:37




    1




    1




    $begingroup$
    @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
    $endgroup$
    – E-mu
    Jan 20 at 10:23






    $begingroup$
    @ShaharMazia I did a bit of searching online, from what I can see it looks like setting up a matrix equation and solving it using the Gaussian elimination algorithm is your best bet, other than randomised algorithms. See mathoverflow.net/questions/6194/….
    $endgroup$
    – E-mu
    Jan 20 at 10:23













    0












    $begingroup$

    Project the new vector on the others and remove.



    If anything remains afterwards then they are linearly independent.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      Project the new vector on the others and remove.



      If anything remains afterwards then they are linearly independent.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        Project the new vector on the others and remove.



        If anything remains afterwards then they are linearly independent.






        share|cite|improve this answer









        $endgroup$



        Project the new vector on the others and remove.



        If anything remains afterwards then they are linearly independent.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 20 at 9:30









        mathreadlermathreadler

        14.9k72262




        14.9k72262






























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