Help: Difficult in optimising these ODE 45 equations

First file

function chisquare = myObjective(P)

a = P(1);

b = P(2);

c = P(3);

d = P(4);

sigma = 180;

hstress = 3463.46;

Hstar = 0.7846;

Kc = 0.1137;

tspan = 0.3722:1:10;

initial_conditions = [0;0;0;0];

[t,y] = ode45(@(t,y)pair1(t,y,a,b,d,hstress,sigma,Hstar,Kc,c),tspan,initial_conditions) %function call

pred=y(:,1);

for i=1:length(t)

expn(i) = exp(i+1)

end

plot(t,expn)

hold on

plot(t,pred)

hold off

chisquare =0;

for i=1:length(pred)

chisquare = chisquare+(pred(i)-expn(i)).^2;

end

end

Second script File

function dy=pair1(t,y,a,b,d,hstress,sigma,Hstar,kc,c)

dy=zeros(4,1);

dy(1) = a*sinh((b*(sigma^d)*(1-y(2)))/((1-y(3))*(1-y(4)))) ;

dy(2) = ((hstress*(a*sinh(b*(sigma^d)*(1-y(2)))/(1-y(3))*(1-y(4))))/(sigma^d))*(1-y(2)/Hstar);

dy(3) = (kc/3)*power((1-y(3)),4);

dy(4) = c*y(1);

end

Third script file

X=csvread('0.18_250MPa.csv');

exp=X(:,2);

P = [0.001 0.1 0.1 0.001];

op = optimiza(P)

Text file is attached below.. Please find the attachment

Ending with the error

Error using myObjective (line 2)

Not enough input arguments.

I suspect I know a bit of what's going wrong.. yet I'm at a loss for how to fix it.. Any help is much appreciated

[Star Strider]

If you are intending to fit your differential equations to data see:

Monod kinetics and curve fitting

How to properly model a kinetic reaction system from experimental data using lsqcurvefit?

There are some others as well, however these are the most illustrative.