How can I fix this error and what does mean by should return 1 or two arguments help pls

% Check userfun
userFG = checkFun(userfun,'SNOPT','userfun');

gotDeriv = 0;
try
  [F,G] = userFG(x);
  gotDeriv = 1;
catch
  try
    F = userFG(x);
    gotDeriv = 0;
  catch
    error('SNOPT:InputArgs','userfun should return 1 or 2 arguments');
  end
end

Error

Error using snopt (line 318)

userfun should return 1 or 2 arguments

Error in Untitled2 (line 173)

[x, f, inform, xmul, fmul] = snopt(xg, xlwr, xupr, xmul, xstate, ...

Answer 1

[Jan]

Which userfcn do you provide? You have to insert changes there, so please post the code of your userfcn.

It should start with

function [output1, output2] = theNameOfYourFcn()
%         ^^^^^^^  ^^^^^^^
end

Answer 2

[Yongjian Feng]

userFG shall return one or two arguments. You can see that the code tries to call userFG and retrieves two returns. If this call throws an exception, then it tries to call userFG and retrieve one retuen. If this also throws exception, then it errors out. So it expects one or two returns.

[Mudrik Ahmed]

What Can I do fix it??

[Yongjian Feng]

So you have validation code and a userFG in discrepancy here basically.

Your validation code shown above requires that a userFG shall return one or two returns. But your userFG returned from the first line does not.

You need to fix this discrepancy.

1. If a userFG indeed needs to return one or two returns, then check your userFG. It shall be something like

function ret1 = your_user_function(x)
% this function returns only one return
end

or

function [ret1, ret2] = your_user_function(x)
% this function returns two returns
end

Use the debugger to step into the first line `userFG = checkFun(userfun,'SNOPT','userfun');` to figure out what userFG is.

2. If a userFG is allowed to return something other than one or two returns then fix your validation code.

[Mudrik Ahmed]

Thanks, I managed to set path for SNOPT and everything just seems sorted apart from other minor errors

[Yongjian Feng]

Great.