lsqnonlin optimset display iter

[hydrantomat]

Hello,

I am trying to solve an ODE and to fit the resulting function to measured
data points with the lsqnonlin function. Variation of the parameter "k"
should fit the function to the data points. This works quite well.

However the optimset function does not display the iterations via
optimset('Display','iter').
Is there something wrong using this function?

Thanks in advance.

%------------- example----------------------------
clear;
% load packages
pkg load optim

% loading measured data
data=[270 0 ;       
                0              5.826    ;       
                10089.25        4.618    ;      
                20510.84        3.84   ;
                41419.94        2.91   ;
                60000       2.4       ;
                83734.16        2.217    ];
        
% data structuring
TR_mes=270; 
t=data(2:end,1);
ygem=data(2:end,2:end);
y0=ygem(1,:);


% differential equiation
function  dxdy= dgl(t,x,k,TK)
dxdy= -(1000 * exp (-k * 1000 / (8.3145 * (TK+273))) ) * x;
endfunction


% start value
strt= 80;

% least square solver
function yTG=lsqnonlinear(k,t,x,ygem,TR) 
[tsim ysim]=ode23('dgl',t,x,k,TR);
yTG= sum(abs(1-(ysim(2:end,:)./ygem(2:end,:))));
endfunction

[xx]= lsqnonlin(@(k)
lsqnonlinear(k,t,y0,ygem,TR_mes),strt,[],[],optimset('Display','iter'));







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