Can someone check my code and rectify me, getting constant output but needs changing.

Can someone check my code and rectify my error.

Here I have given a main code, two functions. On running it gives me constant output but I need that value of 'a' in main function should keep changing with each loop and final value I need like Glc get stored, at end of loop, to plot a variable graph. I have tried to simplify code and added possible change in comments format, but there's still problem. So, I needed help in it. In advance Thanks a lot for helping me out.

clear
close all
clc
M = {'Gal','Urd','Glc','Asn','Amm','Glu','Lac','Gln','Asp'};

v = 100;
cellden = 200000;
mb = 2.76709;
umax = 0.0650;

gal = 0;                   
urd = 0;                   
glc = 36;             
asn = 6.09;            
amm = 0.1;              
glu = 2.125333333;    
lac = 1.391166667;     
gln = 0.01;                
asp = 1.05;            

for k = 1:216
    a = flim(glc,asn);
    b = 2;
    u = umax*a*b;
    udeathf = 3;

    qAmm = 12; 
    qUrd = 19;
    qGln = 15;
    qGlc = -10; 
    qGal = 11;
    qLac = 12;
    qAsn = -13; 
    qAsp = -12; 
    qGlu = -9;;

    tspan = [0 216];
    xo = [100;20000000;0;0;3600;609;10;212.533;139.11667;1;105;276.709];
    [t,X]=ode23s(@(t,X) new_try_func(t,X,v,cellden,mb,u,udeathf,gal,urd,glc,asn,amm,glu,lac,gln,asp,qAmm,qUrd,qGln,qGlc,qGal,qLac,qAsn,qAsp,qGlu),tspan,xo);  
    cd(k) = X(1,2)/X(1,1);
    time(k) = k;
    v = X(1,1);
    
    cellden = X(1,2)/X(1,1);
    gal = X(1,3)/X(1,1);
    urd = X(1,4)/X(1,1);
    glc = X(1,5)/X(1,1);
    asn = X(1,6)/X(1,1);
    amm = X(1,7)/X(1,1);
    glu = X(1,8)/X(1,1);
    lac = X(1,9)/X(1,1);
    gln = X(1,10)/X(1,1);
    asp = X(1,11)/X(1,1);
    mb = X(1,12)/X(1,1);
end
 

%cell_density(:,1) = X(:,2)./X(:,1);
%Gal(:,1) = X(:,3)./X(:,1);
%Urd(:,1) = X(:,4)./X(:,1);
%Glc(:,1) = X(:,5)./X(:,1);
%Asn(:,1) = X(:,6)./X(:,1);
%Amm(:,1) = X(:,7)./X(:,1);
%Glu(:,1) = X(:,8)./X(:,1);
%Lac(:,1) = X(:,9)./X(:,1);
%Gln(:,1) = X(:,10)./X(:,1);
%Asp(:,1) = X(:,11)./X(:,1);
%mAb(:,1) = X(:,12)./X(:,1);

plot(time,cd);  % or plot(cell_density);
xlim([0 216]);

Next are function code in simplified way(not original)

function dydt = new_try_func(~,X,v,cellden,mb,u,udeathf,gal,urd,glc,asn,amm,glu,lac,gln,asp,qAmm,qUrd,qGln,qGlc,qGal,qLac,qAsn,qAsp,qGlu)
    mmAb = 0.410;
    YmAb_X = 3.39;
    dydt = zeros(12,1);
    
    Fin = 0.1;       
    Fout = 0;        

    Gal = 0;         
    Urd = 0;         
    Glc = 144.37;    
    Asn = 26.99;     
    Amm = 0.06;      
    Glu = 12.19;     
    Lac = 16.64;     
    Gln = 0;         
    Asp = 51.95;     
    
    dydt(1,1) = Fin - Fout;                                     % volume
    dydt(2,1) = ((u - udeathf)*v*cellden) - (Fout*cellden);     %cell density
    dydt(3,1) = (Fin*Gal) - (Fout*gal) + (qGal*v*cellden);      % Gal
    dydt(4,1) = (Fin*Urd) - (Fout*urd) + (qUrd*v*cellden);      % Urd
    dydt(5,1) = (Fin*Glc) - (Fout*glc) + (qGlc*v*cellden);      % Glc   
    dydt(6,1) = (Fin*Asn) - (Fout*asn) + (qAsn*v*cellden);      % Asn
    dydt(7,1) = (Fin*Amm) - (Fout*amm) + (qAmm*v*cellden);      % Amm
    dydt(8,1) = (Fin*Glu) - (Fout*glu) + (qGlu*v*cellden);      % Glu
    dydt(9,1) = (Fin*Lac) - (Fout*lac) + (qLac*v*cellden);      % Lac
    dydt(10,1) = (Fin*Gln) - (Fout*gln) + (qGln*v*cellden);     % Gln
    dydt(11,1) = (Fin*Asp) - (Fout*asp) + (qAsp*v*cellden);     % Asp
    dydt(12,1) = (-1*Fout*mb) + ((YmAb_X*u + mmAb)*v*cellden);  %mAb
    
    
    %v = X(1);
    %cellden = X(2)/X(1);
    %gal = X(3)/X(1);
    %urd = X(4)/X(1);
    %glc = X(5)/X(1);
    %asn = X(6)/X(1);
    %amm = X(7)/X(1);
    %glu = X(8)/X(1);
    %lac = X(9)/X(1);
    %gln = X(10)/X(1);
    %asp = X(11)/X(1);
    %mb = X(12)/X(1);
    
        
end

Function for 'a'

function a = flim(glc,asn)
    KGlc = 14;
    KAsn = 2;
	a = ((glc*asn)/((glc + KGlc)*(asn + KAsn)));
end

Answer 1

[Walter Roberson]

    [t,X]=ode23s(@(t,X) new_try_func(t,X,v,cellden,mb,u,udeathf,gal,urd,glc,asn,amm,glu,lac,gln,asp,qAmm,qUrd,qGln,qGlc,qGal,qLac,qAsn,qAsp,qGlu),tspan,xo);  

There is one row of X for each t value. The rows correspond to the X vector at different time steps.

    glc = X(1,5)/X(1,1);

The different rows correspond to the X vector at different time steps. The first row, X(1,:), corresponds to the X values at the first time step. Which is to say, it is always going to be the same as the boundary conditions you pass in.

You are therefore going to be setting the new value of glc the same as what you passed in for the boundary conditions. You are passing in 100 for x0(1) and 3600 for x0(6) so you will get out 3600/100 = 36 which is the same as your initial glc. Nothing can change.

You should be considering extracting from (for example) X(end,5)/X(end,1)

(My internal tracking number for this is T0098912)

[Agrim Singh]

The values are updating now, BUT IT stops updating after t = 24; and becomes constant. Any clues to why???

[Walter Roberson]

glc and asn get up to roughly 1e154, and when that happens their product is infinite and the ratio of two infinite numbers in flim leads to NaN.