Matlab - runge kutta dos ecuaciones

%% runge kutta dos ecuaciones

x1=1

y1=0

h=0.05

t(1)=0;x(1)=x1;y(1)=y1

x(t)=x'

dx'=0.1*(1-x^2)*x'-x

f=j;

g=dw;

F=inline(f,'t','w','j');

G=inline(g,'t','w','j');

fprintf('%10.6f %10.6f %10.6f\n',t(1),w,j);

for i=1

    t(i+1)=t(1)+i*h

    k(1)=h*F(t(i),x(i),y(i));

    l(1)=h*G(t(i),x(i).y(i))

    k(2)=h*F(t(i)+h/2,x(i)+k(1)/2,y(i)+l(1)/2);

    l(2)=h*G(t(i)+h/2,x(i)+k(1)/2,y(i)+l(1)/2);

    k(3)=h*F(t(i)+h/2,x(i)+k(2)/2,y(i)+l(2)/2);

    l(3)=h*G(t(i)+h/2,x(i)+k(2)/2,y(i)+l(2)/2);

    k(4)=h*F(t(i)+h,x(i)+k(3),y(i)+l(3));

    l(4)=h*G(t(i)+h,x(i)+k(3),y(i)+l(3));

    x(i+1)=x(i)+(1/6)*(k(1)+x*k(2)+x*k(3)+k(4));

    y(i+1)=y(i)+(1/6)*(l(1)+2*l(2)+2*l(3)+l(4));

    fprintf('%10.6f %10.6f %10.6f/n',t(i+1),x(i+1),y(i+1));

end

plot(t,x,'r-',t,y,'b-')

%% runge kutta dos ecuaciones

% Necesito una ayuda a como meter las funciones f y g. ya que me arroja error

% las ecuaciones que quiero poner seria

% dx'/dt=0.1*(1-x^2)*x´-x

% que es la de van der pol, ya que necesito gratificarla pero sin usar el comando

clear all

syms t x1 x2

f=x2;

g=0.1*(1-x1^2)*x2-x1;

t0=0; x0=1; y0=0; h=0.05;

t(1)=0; x(1)=x0; y(1)=y0;

a=x0; b=2;   n=(b-a)/h;

F=inline(f,'t','x1','x2');

G=inline(g,'t','x1','x2');

fprintf('%10.6  %10.6f %10.6f\n',t(1),x(1),y(1));

for i=1:n

    k(1)=h*F(t(i),x(i),y(i));

    l(1)=h*G(t(i),x(i),y(i));

    k(2)=h*F(t(i)+h/2,x(i)+k(1)/2,y(i)+l(1)/2);

    l(2)=h*G(t(i)+h/2,x(i)+k(1)/2,y(i)+l(1)/2);

    k(3)=h*F(t(i)+h/2,x(i)+k(2)/2,y(i)+l(2)/2);

    l(3)=h*G(t(i)+h/2,x(i)+k(2)/2,y(i)+l(2)/2);

    k(4)=h*F(t(i)+h,x(i)+k(3),y(i)+l(3));

    l(4)=h*G(t(i)+h,x(i)+k(3),y(i)+l(3));

    x(i+1)=x(i)+(1/6)*(k(1)+2*k(2)+2*k(3)+k(4));

    y(i+1)=y(i)+(1/6)*(l(1)+2*l(2)+2*l(3)+l(4));

     t(i+1)=t(i)+i*h;

    fprintf('%10.2f %10.6f %10.6f\n',t(i+1),x(i+1),y(i+1));

end

plot(t,x,'r-',t,y,'b-')

>> vander_pol_runge_kutta4_1

      0.05   0.998750  -0.049979

      0.15   0.995004  -0.099836

      0.30   0.988771  -0.149451

      0.50   0.980065  -0.198709

      0.75   0.968908  -0.247499

      1.05   0.955325  -0.295716

      1.40   0.939347  -0.343257

      1.80   0.921012  -0.390022

      2.25   0.900360  -0.435919

      2.75   0.877436  -0.480854

      3.30   0.852292  -0.524740

      3.90   0.824981  -0.567491

      4.55   0.795563  -0.609023

      5.25   0.764100  -0.649256

      6.00   0.730660  -0.688109

      6.80   0.695314  -0.725503

      7.65   0.658136  -0.761362

      8.55   0.619204  -0.795607

      9.50   0.578603  -0.828162

     10.50   0.536418  -0.858951