How can i save input prompt for a while loop

Hi i am pretty new to matlab and i was wondering how i can save a "user answer" for a while loop. I mean, so that the question doesn't pop up every time in the loop. The answer to the input should be save throughout the loop.

while det(F) > 0;
    N = N-1000;                 % Initial load decreased

[a, b] = berry(N,E,I,L);        % retrieve a and b
[K1,K2]=LS;                     % 6x6 stiffness matrix fixed-fixed
[beam1,col1]=frame;             %<--- (now it is in this function the input is asked)
F = beam + col; 
det(F);

end

Depending on the input the user gives, the initial 6x6 matrix is scaled down to a 4x4 matrix.

Hope you can help me! =) hehe

Answer 1

[Walter Roberson]

beam_init = false;
while det(F) > 0;
  N = N-1000;                 % Initial load decreased

    [a, b] = berry(N,E,I,L);        % retrieve a and b
    [K1,K2]=LS;                     % 6x6 stiffness matrix fixed-fixed
    if ~beam_init
      [beam1,col1]=frame;             %<--- (now it is in this function the input is asked)
      beam_init = true;
    end
    F = beam + col; 
    det(F);

end