I have a function statement that works in Octave but fails in Matlab

my code in Octave is

for j= 1:12
    I(j)= Io +j*DI;
    j  
    x
    [x  ,fval] = fsolve(@(x) f(x,I(j)), x0, options);
    y1(j)= x(1)
    y2(j)= x(2)
    x0 = x
endfor

plotyy (I , y1 ,  I , y2  )

function [y] =  f( x , I )function [y] =  f( x , I )

MAtlab says

Error: File: CurrentagainstT.m Line: 20 Column: 1
Function definition not supported in this context. Create functions in code file.
What am I supposed to do

[Stephen23]

Also replace endfor with end.

[Walter Roberson]

And you appear to "function" the same thing twice in one line.

[Geoff Taylor]

Here is my complete code below. The word "function" only appears once on the line, and both "for" loop and "function" module end with "end" statement. This code works well in GNU Octave. However I get the MATLAB error

Error: File: CurrentagainstT.m Line: 97 Column: 1

Function definitions in a script must appear at the end of the file.

Move all statements after the "f" function definition to before the first local function definition.

options=optimset('Display','iter');
x0=[310 ; 0.001 ]; Io=1e-3; DI=1.5e-3;
maxiter = 12;
x = zeros(1, maxiter);
fval = zeros(1, maxiter);

for j= 1:12
    I(j)= Io +j*DI;
    j  
    x
    [x  ,fval] = fsolve(@(x) f(x,I(j)), x0, options);
    y1(j)= x(1)
    y2(j)= x(2)
    x0 = x
end

plotyy (I , y1 ,  I , y2  )

function y =  f( x , I )
m=5 ; D=0.9e-3; E1n=0.03 ; E1p=0.01 ; phit =0 ; phib =0; m1 = 3 ; ar=5e-4;
co=3e10 ; lamda=0.98e-4 ; ngaas= 3.6; gamma=0.069; ngo=3.27;
To=300;Rdo=80;
R=0.997;alpha=15;Lc=0.4298e-4;q=1.6e-19; vg=8e9;
h=6.6e-34;mo=9e-31;k=1.38e-23;hb=h/2/pi;kb=k/q;kT=k*To;
Nc=5e17;Nv=7e18;xn=1e-5;xp=1e-5;Aein = 1.5e-10;
Bbar= (Aein/(8*pi))*(lamda/ngaas)^2*(co/ngaas);
mn=0.067;mp=0.45;Dp=1e-4*mp*mo/pi/hb^2;Dn=1e-4*mn*mo/pi/hb^2;Lz=0.6e-6;
Dnp=Dn*Dp ;
tauinv=vg*(log(1/R)/Lc + alpha); taup =1/tauinv;
taupp=gamma*taup;
Kpar = Lz^2/(m*taupp*h*Dnp*Bbar*kT) ;   
z1= 2*exp(2*Kpar);
EFtm=2*(kT/q)*log(z1-1+sqrt((z1-1)^2-1)) ;
dEg=0.3;EFn=EFtm/2;EFp=EFtm/2; Ego= 1.30 -5.6e-4 *To^2/(204+To);
Egeff=    E1n +E1p + Ego;
ng =  ngo+ar*To ;                 
hv1 = h*co*(m1-(phit+phib))/(2*q*Lc*ng) ;
hv= hv1 - Egeff  ;
Vj=Egeff+EFtm  ;

nth=Dn*EFn*q/Lz ;

t1=x(1);
Rd = Rdo +0.083*(x(1)-To);

A=(pi/4)*D.^2;

tnr=1e-9;q=1.6e-19;Jqw=q*m*Lz*nth/tnr;
Rjo= 2000;Rjp=5 ;Rj= Rjo + Rjp*(x(1)-To); 

Jtr=q*((xn+xp)/tnr/2)*sqrt(Nc*Nv)*exp(-(dEg-(E1n+E1p)-EFtm)/(2*kb*x(1)))
Jth=Jtr+Jqw;Ith=A*Jth
etae=Jqw/Jth ;
etao=log(1/R)/(alpha*Lc+log(1/R));
etas= (Egeff+hv)*etae*etao;
t2=I

delT=(I.^2*Rd+I*Vj-x(2))*Rj

y(1) = x(1) - To  - delT

y(2) = x(2)-(I-Ith)*etas
 
x(1)
x(2)  

end

Answer 1

[Star Strider]

In most instances, only anonymous functions can occur in a script file in MATLAB.

The documentation section on Create Functions in Files notes tthat:

• Starting in R2016b, another option for storing functions is to include them at the end of a script file.

so it is possible, with some restrictions. See the cited (and related) documentation for details.