I understand this question has been asked before but for some reason I can't get it to work also I'm new to stackexchage so I apologize if everything I write is not up to standards. That being While[procedure;test] In the code I'm currently working on I'm trying to make a matrix but only if it makes certain conditions. The Code as it currently stands is x=Table[RandomChoice[{1-alpha*E^(-1/Total[listA]),alpha,alpha*E^(-1/Total[listA]}->{-1,0,1}]*ListB[[i]]*ListB[[j]],{i,Length[ListB]},{j,Length[ListB]}] and I'm trying to make the code cycle through till it hits condition of Det[%]>0

  • 1
    $\begingroup$ Would it be possible to give the full code that you are using and what your are hoping for as an output? It is not too clear from your question? $\endgroup$
    – Dunlop
    Commented Nov 3, 2016 at 20:45
  • $\begingroup$ I'm trying to get a table where the Det is a positive number. both List A and list B are simple lists, there is nothing complicated about them. $\endgroup$
    – Wilco
    Commented Nov 3, 2016 at 20:53
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    $\begingroup$ Did you try While[x = Table[...]; Det[x] <= 0]? $\endgroup$ Commented Nov 3, 2016 at 21:27

1 Answer 1


I've just made up listA and listB:

listA = {1, 2, 3, 4, 5};
listB = {8, 7, 6, 5, 4}; alpha = 1; 
x := Table[RandomChoice[{1 - alpha*E^(-1/Total[listA]), alpha, 
      alpha*E^(-1/Total[listA])} -> {-1, 0, 1}]*listB[[i]]*
      listB[[j]], {i, Length[listB]}, {j, Length[listB]}]
While[m = x; Det[m] <= 0];

The final m is a matrix with positive Det. Because of the := definition, each time through the While, a different m is produced.


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