Too Many Output Arguments fseminf

I am using a solution to a problem involving fitting a curve to only two points, found here: https://www.mathworks.com/matlabcentral/answers/159931-given-two-points-fit-a-curve#answer_156452

However, using this solution with a few minor changes results in

Error using find_sweep_polynomials>myinfcon

Too many output arguments.

My code is as such:

f=@cubic;                      %functions of (p,x)
df=@dcubic;

x0 = 0;
xn = 12;

y0= 0;
yn = 1;

p0 = [1, 1, 1];

cf = @(p,x)  (f(p,x0)-y0)^2 + (f(p,xn)-yn)^2;
[x, fval] = fseminf(cf, p0, 1, @(p,S) myinfcon(p,S,x0,xn,y0,yn,df))

Error using solution>myinfcon
Too many output arguments.

Error in solution>@(p,S)myinfcon(p,S,x0,xn,y0,yn,df) (line 13)
[x, fval] = fseminf(cf, p0, 1, @(p,S) myinfcon(p,S,x0,xn,y0,yn,df))

Error in fseminf (line 463)
[ctmp,ceqtmp,~,~] = feval(userconfcn{3},x,s,varargin{:});

Caused by:
Failure in initial evaluation of semi-infinite constraint function (seminfcon). FSEMINF cannot continue.

function [c,ceq,K1] = myinfcon(p,S,x0,xn,y0,yn,df)
c=[]; ceq=[];
if isnan(S)
    S=[(xn-x0)/10,  0];
end
w=x0:S(1):xn;
K1=sign(y0-yn)*df(p,w);
end

function out = cubic(p, x)

out = p(1)*x.^3 + p(2)*x.^2 + p(3)*x;

end

function out = dcubic(p, x)

out = 3*p(1)*x.^2 + 2*p(2)*x + p(3);

end

I checked the documentation and there should be nothing wrong with this syntax, especially since I took it from an expert on these forums. I don't believe I am redefining any existing matlab functions, and there is no issue with there being files elsewhere because this is all self-contained in one script.

Answer 1

[Image Analyst]

Maybe try not defining your anonymous function inside the argument list of the function you're trying to call. So instead of

[x, fval] = fseminf(cf, p0, 1, @(p,S) myinfcon(p,S,x0,xn,y0,yn,df))

try

func = @(p,S) myinfcon(p,S,x0,xn,y0,yn,df)) % Define an anonymous function.
fValue = func(p,S,x0,xn,y0,yn,df) % Get the value for a set of inputs.
[x, fval] = fseminf(cf, p0, 1, fValue) % Pass that value into the fseminf() function.

[Carleen McKenna]

There is no variable "p" or "S" defined in my script and those variables are not defined until fseminf is run, so I don't understand how this helps. I tried your suggestion anyway and predictably got "Unrecognized function or variable 'p'."

In addition, if I remove the "fValue" line and just use "func" in fseminf, I get the same issue.

[Carleen McKenna]

Nevermind. The issue was not with the function call. Apparently I needed to also output "S" in myinfcon. I thought this was optional due to the way it was written in the example I linked in my original question. This problem is solved.