how can i solve these errors in matlab code?

Hi all,

when I use the function "nlinfit" to find the parameters of a second order system, these errors are appeared:

??? Error using ==> nlinfit>checkFunVals at 357 MODELFUN has returned Inf or NaN values.

Error in ==> nlinfit>LMfit at 304 if funValCheck && ~isfinite(sse), checkFunVals(r); end

Error in ==> nlinfit at 167 [beta,J,lsiter,cause] = LMfit(X,y, model,beta,options,verbose,maxiter);

...................................... the Matlab code is: -------------------------------------- function mdl =MyModelisation(x,y)

model=@(p,t) p(1).*(1-exp(-p(2).*p(3).*t).*sin(p(3)*sqrt(1-p(2)^p(2)).*t./sqrt(1-p(2)^2)+asin(sqrt(1-p(2)^2))));

beta= EstimG(y); mdl=nlinfit(x,y,model,beta);

thank you in advence

end

function g= EstimG(x)

n = find(diff(diff(x) > 0) < 0); u = find(x(n+1) > x(n)); n(u) = n(u)+1; moy=0; pic=n(3) for i=pic:length(x) moy=moy+x(i); end moy=moy/(length(x)-n(3)+1);

delta=u(2)-u(1); delta=delta/10; % en seconde zeta=0.3; wd=2*pi/delta; wn=wd/sqrt(1-zeta^2); g=[moy, zeta, wn] end ----------------------------------

how cqan I solve this errors?

thank you