Why is "fitoptions" returning the error "Too many input arguments"?

I have defined the function 'BTKcon' and saved it in an .m file as seen below.

function [con] = BTKcon(Gamma,Delta,Z,T,V)
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here

u0Sq=@(Gamma,Delta,En)(1/2)*(1+(sqrt(((abs(En)+1i*Gamma).^2)-(Delta.^2))./(abs(En)+1i*Gamma))); 
v0Sq=@(Gamma,Delta,En)(1/2)*(1-(sqrt(((abs(En)+1i*Gamma).^2)-(Delta.^2))./(abs(En)+1i*Gamma)));

alpha=@(Gamma,Delta,En)real(u0Sq(Gamma,Delta,En));
etta=@(Gamma,Delta,En)imag(u0Sq(Gamma,Delta,En));
betta=@(Gamma,Delta,En)real(v0Sq(Gamma,Delta,En));
gammaSq=@(Gamma,Delta,Z,En)((alpha(Gamma,Delta,En)+(Z.^2).*(alpha(Gamma,Delta,En)...
    -betta(Gamma,Delta,En))).^2)+((etta(Gamma,Delta,En).*(2.*(Z.^2)+1))).^2;

BTKA=@(Gamma,Delta,Z,En)sqrt(((alpha(Gamma,Delta,En).^2)+(etta(Gamma,Delta,En).^2)).*((betta(Gamma,Delta,En).^2)...
    +(etta(Gamma,Delta,En).^2)))./gammaSq(Gamma,Delta,Z,En);

BTKB=@(Gamma,Delta,Z,En)((Z.^2).*((((alpha(Gamma,Delta,En)-betta(Gamma,Delta,En)).*Z-2.*etta(Gamma,Delta,En)).^2)...
    +((2.*Z.*etta(Gamma,Delta,En)+(alpha(Gamma,Delta,En)-betta(Gamma,Delta,En))).^2)))./gammaSq(Gamma,Delta,Z,En);

dFermi=@(E,V,T)11600.928.*exp(11600.928.*(E-V)./T)./(((1+exp(11600.928.*(E-V)./T)).^2).*T);

con = (1+Z.^2).*integral(@(E) real(dFermi(E,V,T).*(1+BTKA(Gamma,Delta,Z,E)-BTKB(Gamma,Delta,Z,E))),...
    -0.015,0.015,ArrayValued=true);
end

I am able to define a 'fittype' using the above function.

ft = fittype('BTKcon( Gamma, Delta, Z, T, V)','independent',{'V'},'coefficients',{'Gamma','Delta','Z','T'})

However, when I try to use 'fitoptions' to define starting points or bounds on my coefficients (e.g., using the command below), I keep getting the error "Too many input arguments".

options = fitoptions(ft, 'Lower', [0.00001 0.0001 0 0.02])

Can someone help me see what I am doing wrong?

Answer 1

[Torsten]

fitoptions is part of fittype, not vice versa as you try to do. Thus fitoptions must be define before fittype:

options = fitoptions('Lower', [0.00001 0.0001 0 0.02]);
ft = fittype('BTKcon( Gamma, Delta, Z, T, V)','independent',{'V'},'coefficients',{'Gamma','Delta','Z','T'},options);

See the example under

https://de.mathworks.com/help/curvefit/fit.html

Chapter Create Fit Options and Fit Type Before Fitting

[Zachary]

Thank you!