Variable ... is undefined on some execution paths

hello guys!

I hope somebody can advise me with respect the next code, when I run it into embedded editor from simulink embedded block, I have the error that Variable 'mu1' is undefined on some execution paths.

function [u_F,mu12,mu32] = fcn(s,delta)
%#codegen

a = 0.5;
mu12 = 0;
mu32 = 0;

      y = 0;
      if s <= -a
          mu1 = 1;
          mu2 = 0;
          mu3 = 0;
      elseif -a < s && s <= 0
          mu1 = -1/a*s;
          mu2 = 1/a*(s+a);
          mu3 = 0;
      elseif s > 0 && a >= s
          mu1 = 0;
          mu2 = -1/a*(s-a);
          mu3 = 1/a*s;
      elseif s > a
          mu1 = 0;
          mu2 = 0;
          mu3 = 1;
      end
      mu12 = mu1;
      mu32 = mu3;
      y = (mu1*(-delta)+mu2*0+mu3*delta)/(mu1+mu2+mu3);
  u_F = y;

Answer 1

[Ryan Livingston]

As the error says, there is a possible execution path on which mu1 is not defined. In particular, if all of the conditions in your if and elseif statements are false, then mu1,mu2,mu3 will not be defined.

To resolve this define them to default values either before the if:

    mu1 = 0; mu2 = 0; mu3 = 0;
    if s<= -1 ...

or add an else branch:

    elseif s > a
        mu1 = 0;
        mu2 = 0;
        mu3 = 1;
    else
        mu1 = 0;
        mu2 = 0;
        mu3 = 0;
    end

The documentation explains this error message in more detail.

[Smaghuli]

Thank you. I already find that by adding else the problem can be solved. But this does not work on MATLAB 2008a. I I tested the model on 2013a and it worked. I will try giving initial values before the conditional statement to see it can solve the problem in older version.

[Ambe Harrison]

Thank you Ryan Livingston your comment was very useful. It just solved a similar problem i encoutered.

Kind regards.

[Elisa Micaela Rodriguez Steinbrecher]

Amazing, thanks for your answer