Output argument m_dot_B is not assigned on some execution paths

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suzlan 2013-11-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106479-output-argument-m_dot_b-is-not-assigned-on-some-execution-paths

评论： suzlan 2013-11-17

error_n.jpg

Hello guys, I have a question about Matlab. When i run the simulation, Matlab give instruction " Output argument is not assigned on some execution path. Below my coding that i using in matlab and im using "matlab function" block. Hope you can help me Thank you

function m_dot_B = fcn(Av, PB) %#codegen

k = 1.4; Cf=0.7; T=294.5; C1=0.0404; C2=0.1562; Pcr=0.528; Ps=5*exp(5);

if PB/Ps <= Pcr

m_dot_B = Cf*Av*C1*(Ps/T^(1/2));

elseif PB/Ps > Pcr

    m_dot_B = Cf*Av*C2*(Ps/T^(1/2)*((PB/Ps)^(1/k))*(1-(PB/Ps)^((k-1)/k))^(1/2));
end

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Answer 1

Image Analyst 2013-11-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106479-output-argument-m_dot_b-is-not-assigned-on-some-execution-paths#answer_115489

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It's possible that neither of your if tests will be true, and if that happens, then fcn would return without having set anything for m_dot_B. A more robust way to write the code would be like this:

function m_dot_B = fcn(Av, PB) %#codegen
% Initialize output in case something goes wrong.
m_dot_B = 0;
try
  k = 1.4;
  Cf=0.7;
  T=294.5;
  C1=0.0404;
  C2=0.1562;
  Pcr=0.528;
  Ps=5*exp(5);
  
  if PB/Ps <= Pcr
    m_dot_B = Cf*Av*C1*(Ps/T^(1/2));
  else
    m_dot_B = Cf*Av*C2*(Ps/T^(1/2)*((PB/Ps)^(1/k))*(1-(PB/Ps)^((k-1)/k))^(1/2));
  end
catch ME
  errorMessage = sprintf('Error in function %s() at line %d.\n\nError Message:\n%s', ...
    ME.stack(1).name, ME.stack(1).line, ME.message);
  fprintf(1, '%s\n', errorMessage);
  uiwait(warndlg(errorMessage);
end